Resizing Audience during workspace-overview can cause a situation in which Gala is unable to run

[Raphael Isemann]

Steps to reproduce:

* Set bottom-right active-corner to "workspace overview"
* Open Audience while Gala is running.
* Grab the bottom-right corner of Audience and start resizing the window.
* Keep the mouse-button pressed (aka, continue scaling) and move to the bottom-right corner of the monitor to activate the active corner.
* You can now continue resize during the window-overview.
* Now move the mouse to the upper left without stopping resizing
* Audience should freak out and when you stop resizing Gala crashes
* After that Gala no longer launches as the Audience window seems to be corrupted and it fails with [1]

Expected behavior:

* You shouldn't be able to rescale Audience during workspace overview in the first place.

Notes:

* It only happens with Audience. Probably due to Audience thing with keeping the aspect ratio of the move in sync with the window-size.

[1]

(gala:29336): GLib-GObject-WARNING **: g_object_set_valist: object class 'ClutterSettings' has no property named 'window-scaling-factor'
Fensterverwalter-Warnung:Log level 128: Settings.vala:158: Loading settings from schema 'org.gnome.desktop.background'
Fensterverwalter-Warnung:Log level 128: Settings.vala:158: Loading settings from schema 'org.pantheon.desktop.gala.keybindings'
Fensterverwalter-Warnung:Log level 128: Settings.vala:158: Loading settings from schema 'org.pantheon.desktop.gala.shadows'
Fensterverwalter-Warnung:Log level 128: Settings.vala:158: Loading settings from schema 'org.pantheon.desktop.gala.behavior'
Fensterverwalter-Warnung:Log level 128: PluginManager.vala:132: Loaded plugin Notify (libgala-notify.so)
Fensterverwalter-Warnung:Log level 128: PluginManager.vala:132: Loaded plugin Zoom (libgala-zoom.so)
Fensterverwalter-Warnung:Log level 8: granite_drawing_buffer_surface_construct: assertion '(_tmp0_ >= 0) && (_tmp1_ >= 0)' failed
Fensterverwalter-Warnung:Log level 8: granite_drawing_buffer_surface_get_context: assertion 'self != NULL' failed
Segmentation fault (core dumped)