Qt: Fix crash when clicking past last tile in viewer

CHANGES

@@ -43,6 +43,7 @@ Other fixes:
  - GB, GBA: Save writeback-pending masked saves on unload (fixes mgba.io/i/2396)
  - mGUI: Fix FPS counter after closing menu
  - Qt: Fix some hangs when using the debugger console
+ - Qt: Fix crash when clicking past last tile in viewer
  - VFS: Failed file mapping should return NULL on POSIX
 Misc:
  - Core: Suspend runloop when a core crashes

src/platform/qt/TilePainter.cpp

@@ -41,7 +41,10 @@ void TilePainter::resizeEvent(QResizeEvent*) {
 void TilePainter::mousePressEvent(QMouseEvent* event) {
 	int x = event->x() / m_size;
 	int y = event->y() / m_size;
-	emit indexPressed(y * (width() / m_size) + x);
+	int index = y * (width() / m_size) + x;
+	if (index < m_tileCount) {
+		emit indexPressed(index);
+	}
 }
 
 void TilePainter::clearTile(int index) {