Qt: Fix opening in fullscreen (fixes #993)

CHANGES

@@ -51,6 +51,7 @@ Bugfixes:
  - GB Timer: Minor accuracy improvements
  - GB Audio: Clock frame events on DIV
  - GBA: Fix SharkPort saves for EEPROM games
+ - Qt: Fix opening in fullscreen (fixes mgba.io/i/993)
 Misc:
  - GBA Timer: Use global cycles for timers
  - GBA: Extend oddly-sized ROMs to full address space (fixes mgba.io/i/722)

src/platform/qt/Window.cpp

@@ -186,7 +186,9 @@ void Window::resizeFrame(const QSize& size) {
 	m_screenWidget->setSizeHint(newSize);
 	newSize -= m_screenWidget->size();
 	newSize += this->size();
-	resize(newSize);
+	if (!isFullScreen()) {
+		resize(newSize);
+	}
 }
 
 void Window::setConfig(ConfigController* config) {