virtio-gpu-gl-pci console tries to make GL context before widget is realized leading to crash
Description of problem:
When `-vga none` is added to the command line, there is no crash.

When it is not, two `GtkGLArea` widgets are created: one for VGA and one for `virtio-gpu-gl-pci`. Only the first one is realized, but the virgl code tries to create a GL context for the second. In `gd_gl_area_create_context`, `gtk_widget_get_window(vc->gfx.drawing_area)` evaluates to NULL a crash follows:

```
qemu: Gdk: gdk_window_create_gl_context: assertion 'GDK_IS_WINDOW (window)' failed
qemu: Gdk: gdk_gl_context_set_required_version: assertion 'GDK_IS_GL_CONTEXT (context)' failed
qemu: Gdk: gdk_gl_context_realize: assertion 'GDK_IS_GL_CONTEXT (context)' failed
qemu: Gdk: gdk_gl_context_make_current: assertion 'GDK_IS_GL_CONTEXT (context)' failed
qemu: Gdk: gdk_gl_context_get_version: assertion 'GDK_IS_GL_CONTEXT (context)' failed
qemu: Gtk: gtk_gl_area_make_current: assertion 'gtk_widget_get_realized (widget)' failed
qemu: Gdk: gdk_window_create_gl_context: assertion 'GDK_IS_WINDOW (window)' failed
qemu: Gdk: gdk_gl_context_set_required_version: assertion 'GDK_IS_GL_CONTEXT (context)' failed
qemu: Gdk: gdk_gl_context_realize: assertion 'GDK_IS_GL_CONTEXT (context)' failed
qemu: Gdk: gdk_gl_context_make_current: assertion 'GDK_IS_GL_CONTEXT (context)' failed
qemu: Gdk: gdk_gl_context_get_version: assertion 'GDK_IS_GL_CONTEXT (context)' failed
qemu: Gtk: gtk_gl_area_make_current: assertion 'gtk_widget_get_realized (widget)' failed
qemu: Gdk: gdk_window_create_gl_context: assertion 'GDK_IS_WINDOW (window)' failed
qemu: Gdk: gdk_gl_context_set_required_version: assertion 'GDK_IS_GL_CONTEXT (context)' failed
qemu: Gdk: gdk_gl_context_realize: assertion 'GDK_IS_GL_CONTEXT (context)' failed
qemu: Gdk: gdk_gl_context_make_current: assertion 'GDK_IS_GL_CONTEXT (context)' failed
qemu: Gdk: gdk_gl_context_get_version: assertion 'GDK_IS_GL_CONTEXT (context)' failed
qemu: Gtk: gtk_gl_area_make_current: assertion 'gtk_widget_get_realized (widget)' failed
qemu: Gdk: gdk_window_create_gl_context: assertion 'GDK_IS_WINDOW (window)' failed
qemu: Gdk: gdk_gl_context_set_required_version: assertion 'GDK_IS_GL_CONTEXT (context)' failed
qemu: Gdk: gdk_gl_context_realize: assertion 'GDK_IS_GL_CONTEXT (context)' failed
qemu: Gdk: gdk_gl_context_make_current: assertion 'GDK_IS_GL_CONTEXT (context)' failed
qemu: Gdk: gdk_gl_context_get_version: assertion 'GDK_IS_GL_CONTEXT (context)' failed
qemu: Gtk: gtk_gl_area_make_current: assertion 'gtk_widget_get_realized (widget)' failed
qemu: Gdk: gdk_window_create_gl_context: assertion 'GDK_IS_WINDOW (window)' failed
qemu: Gdk: gdk_gl_context_set_required_version: assertion 'GDK_IS_GL_CONTEXT (context)' failed
qemu: Gdk: gdk_gl_context_realize: assertion 'GDK_IS_GL_CONTEXT (context)' failed
qemu: Gdk: gdk_gl_context_make_current: assertion 'GDK_IS_GL_CONTEXT (context)' failed
qemu: Gdk: gdk_gl_context_get_version: assertion 'GDK_IS_GL_CONTEXT (context)' failed
qemu: Gtk: gtk_gl_area_make_current: assertion 'gtk_widget_get_realized (widget)' failed
qemu: Gdk: gdk_window_create_gl_context: assertion 'GDK_IS_WINDOW (window)' failed
qemu: Gdk: gdk_gl_context_set_required_version: assertion 'GDK_IS_GL_CONTEXT (context)' failed
qemu: Gdk: gdk_gl_context_realize: assertion 'GDK_IS_GL_CONTEXT (context)' failed
qemu: Gdk: gdk_gl_context_make_current: assertion 'GDK_IS_GL_CONTEXT (context)' failed
qemu: Gdk: gdk_gl_context_get_version: assertion 'GDK_IS_GL_CONTEXT (context)' failed
qemu: Gtk: gtk_gl_area_make_current: assertion 'gtk_widget_get_realized (widget)' failed
qemu: Gdk: gdk_window_create_gl_context: assertion 'GDK_IS_WINDOW (window)' failed
qemu: Gdk: gdk_gl_context_set_required_version: assertion 'GDK_IS_GL_CONTEXT (context)' failed
qemu: Gdk: gdk_gl_context_realize: assertion 'GDK_IS_GL_CONTEXT (context)' failed
qemu: Gdk: gdk_gl_context_make_current: assertion 'GDK_IS_GL_CONTEXT (context)' failed
qemu: Gdk: gdk_gl_context_get_version: assertion 'GDK_IS_GL_CONTEXT (context)' failed
qemu: Gtk: gtk_gl_area_make_current: assertion 'gtk_widget_get_realized (widget)' failed
qemu: Gdk: gdk_window_create_gl_context: assertion 'GDK_IS_WINDOW (window)' failed
qemu: Gdk: gdk_gl_context_set_required_version: assertion 'GDK_IS_GL_CONTEXT (context)' failed
qemu: Gdk: gdk_gl_context_realize: assertion 'GDK_IS_GL_CONTEXT (context)' failed
qemu: Gdk: gdk_gl_context_make_current: assertion 'GDK_IS_GL_CONTEXT (context)' failed
qemu: Gdk: gdk_gl_context_get_version: assertion 'GDK_IS_GL_CONTEXT (context)' failed
qemu: Gtk: gtk_gl_area_make_current: assertion 'gtk_widget_get_realized (widget)' failed
qemu: Gdk: gdk_window_create_gl_context: assertion 'GDK_IS_WINDOW (window)' failed
qemu: Gdk: gdk_gl_context_set_required_version: assertion 'GDK_IS_GL_CONTEXT (context)' failed
qemu: Gdk: gdk_gl_context_realize: assertion 'GDK_IS_GL_CONTEXT (context)' failed
qemu: Gdk: gdk_gl_context_make_current: assertion 'GDK_IS_GL_CONTEXT (context)' failed
qemu: Gdk: gdk_gl_context_get_version: assertion 'GDK_IS_GL_CONTEXT (context)' failed
qemu: Gtk: gtk_gl_area_make_current: assertion 'gtk_widget_get_realized (widget)' failed
qemu: Gdk: gdk_window_create_gl_context: assertion 'GDK_IS_WINDOW (window)' failed
qemu: Gdk: gdk_gl_context_set_required_version: assertion 'GDK_IS_GL_CONTEXT (context)' failed
qemu: Gdk: gdk_gl_context_realize: assertion 'GDK_IS_GL_CONTEXT (context)' failed
qemu: Gdk: gdk_gl_context_make_current: assertion 'GDK_IS_GL_CONTEXT (context)' failed
qemu: Gdk: gdk_gl_context_get_version: assertion 'GDK_IS_GL_CONTEXT (context)' failed
qemu: Gtk: gtk_gl_area_make_current: assertion 'gtk_widget_get_realized (widget)' failed
qemu: Gdk: gdk_window_create_gl_context: assertion 'GDK_IS_WINDOW (window)' failed
qemu: Gdk: gdk_gl_context_set_required_version: assertion 'GDK_IS_GL_CONTEXT (context)' failed
qemu: Gdk: gdk_gl_context_realize: assertion 'GDK_IS_GL_CONTEXT (context)' failed
qemu: Gdk: gdk_gl_context_make_current: assertion 'GDK_IS_GL_CONTEXT (context)' failed
qemu: Gdk: gdk_gl_context_get_version: assertion 'GDK_IS_GL_CONTEXT (context)' failed
qemu: Gtk: gtk_gl_area_make_current: assertion 'gtk_widget_get_realized (widget)' failed
qemu: Gdk: gdk_gl_context_make_current: assertion 'GDK_IS_GL_CONTEXT (context)' failed
gl_version 0 - compat profile
WARNING: running without ARB/KHR robustness in place may crash
qemu-system-x86_64: ../libepoxy/src/dispatch_common.c:872: epoxy_get_proc_address: Assertion `0 && "Couldn't find current GLX or EGL context.\n"' failed.
```
Steps to reproduce:
1. Get OVMF. On Arch Linux, you can install the `edk2-ovmf` package. On other distros, find a similar package and modify the path in the command accordingly.
2. Run the command above.