window_size plugin crash during app destroy process

[imReker]

When app is going to destroy (eg, close the window), it'll crash at:

flutter-desktop-embedding/plugins/window_size/windows/window_size_plugin.cpp

Line 181 in 8ea9f1c

registrar_->UnregisterTopLevelWindowProcDelegate(window_proc_id_);

When RegisterTopLevelWindowProcDelegate, the PluginRegistrarWindows store the delegate in it's member:window_proc_delegates_, and it seems like PluginRegistrarWindows destructed window_proc_delegates_ before destruct the plugin. So, when the plugin tries to UnregisterTopLevelWindowProcDelegate, the std::map is already destroyed and lead to crash.

[stuartmorgan-g]

Good catch, thanks for the report. This is actually a bug in the client_wrapper code in flutter/engine rather than the plugin itself, since the registrar is supposed to be valid for the entire lifetime of the plugin.