Fixes error during bootup
When Gnome-Shell is launched from GDM3 and has Desktop Icons, this error is shown in the output:
(gnome-shell.bin:6393): Gjs-CRITICAL **: 18:13:23.999: Object St.Widget (0x5648ac6b7150), has been already deallocated - impossible to access to it. This might be caused by the fact that the object has been destroyed from C code using something such as destroy(), dispose(), or remove() vfuncs
== Stack trace for context 0x5648aa7af320 ==
(gnome-shell.bin:6393): Gjs-CRITICAL **: 18:13:24.294: Object St.Widget (0x5648ac7d8a10), has been already deallocated - impossible to access to it. This might be caused by the fact that the object has been destroyed from C code using something such as destroy(), dispose(), or remove() vfuncs
== Stack trace for context 0x5648aa7af320 ==
This only happens during the first bootup; using Alt+F2 and 'r' doesn't trigger it.
To fix this, it is proposed to track whether the actor has been already destroyed, and avoid calling destroy() in that case.