Don't deinit SDL from non-SDL thread

src/panda_qt/main_window.cpp

@@ -211,8 +211,6 @@ void MainWindow::closeEvent(QCloseEvent *event) {
 	if (emuThread.joinable()) {
 		emuThread.join();
 	}
-
-	SDL_Quit();
 }
 
 // Cleanup when the main window closes
@@ -602,4 +600,4 @@ void MainWindow::pollControllers() {
 			}
 		}
 	}
-}
+}