Give a timeslice to show Save Changes? dialog before things get ugly.

This also moves closing the existing project earlier to improve the
workflow -- so there's a chance that the main fix might not be needed
anymore, but it's still safer to not have a control-flow that crashes
rather than to just not use that control-flow.

Fixes https://gitlab.com/kicad/code/kicad/issues/9200

kicad/import_project.cpp

@@ -66,6 +66,11 @@ void KICAD_MANAGER_FRAME::ImportNonKiCadProject( const wxString& aWindowTitle,
     if( schdlg.ShowModal() == wxID_CANCEL )
         return;
 
+    // OK, we got a new project to open.  Time to close any existing project before we go on
+    // to collect info about where to put the new one, etc.  Otherwise the workflow is kind of
+    // disjoint.
+    CloseProject( true );
+
     wxFileName sch( schdlg.GetPath() );
     sch.SetExt( aSchFileExtension );
 
@@ -171,8 +176,6 @@ void KICAD_MANAGER_FRAME::ImportNonKiCadProject( const wxString& aWindowTitle,
         }
     }
 
-    // Close the project and make the new one
-    CloseProject( true );
     CreateNewProject( pro.GetFullPath(), false /* Don't create stub files */ );
     LoadProject( pro );
 

kicad/kicad_manager_frame.cpp

@@ -411,6 +411,9 @@ bool KICAD_MANAGER_FRAME::CloseProject( bool aSave )
     if( !Kiway().PlayersClose( false ) )
         return false;
 
+    // Give a timeslice for the save-changes? dialog (and for the project to actually close)
+    wxSafeYield();
+
     // Save the project file for the currently loaded project.
     if( m_active_project )
     {