Don't destroy the DIALOG_PCM_PROGRESS until after the threads actually terminated

(cherry picked from commit 47cf26f047)

kicad/pcm/pcm_task_manager.cpp

@@ -642,13 +642,16 @@ void PCM_TASK_MANAGER::RunQueue( wxWindow* aParent )
             } );
 
     m_reporter->KeepRefreshing( true );
+
+    download_thread.join();
+    install_thread.join();
+
+    // Destroy the reporter only after the threads joined
+    // Incase the reporter terminated due to cancellation
     m_reporter->Destroy();
     m_reporter.reset();
 
     aParent->Raise();
-
-    download_thread.join();
-    install_thread.join();
 }