SaveTool: fix a segfault.

src/SaveTool/SaveTool.cpp

@@ -375,6 +375,11 @@ void SaveTool::updateCheckEvent(SDL_Event& event) {
 }
 
 void SaveTool::fileUpdateEvent(SDL_Event& event) {
+    if(event.user.code == StagedUpdate) {
+        _massManager->refreshStagedMasses();
+        return;
+    }
+
     Containers::String filename{static_cast<char*>(event.user.data1), std::strlen(static_cast<char*>(event.user.data1)), nullptr};
     Containers::String old_filename;
 
@@ -444,9 +449,6 @@ void SaveTool::fileUpdateEvent(SDL_Event& event) {
                 }
             }
             break;
-        case StagedUpdate:
-            _massManager->refreshStagedMasses();
-            break;
         default:
             _queue.addToast(Toast::Type::Warning, "Unknown file action type"_s);
     }