KiWay: Make sure to mark closed windows as closed

Also make sure to veto project import if we couldn't close the existing project.

Fixes https://gitlab.com/kicad/code/kicad/-/issues/13215

Maybe also fixes some other weird crashes, we'll see.

common/kiway.cpp

@@ -466,7 +466,10 @@ bool KIWAY::PlayerClose( FRAME_T aFrameType, bool doForce )
         return true;
 
     if( frame->NonUserClose( doForce ) )
+    {
+        m_playerFrameId[aFrameType] = wxID_NONE;
         return true;
+    }
 
     return false;
 }

kicad/import_project.cpp

@@ -60,7 +60,8 @@ void KICAD_MANAGER_FRAME::ImportNonKiCadProject( const wxString& aWindowTitle,
     // 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 );
+    if( !CloseProject( true ) )
+        return;
 
     IMPORT_PROJ_HELPER importProj( this, schdlg.GetPath(), aSchFileExtension, aPcbFileExtension );