UI: Fix crash when systray is not enabled

UI/window-basic-main.cpp

@@ -6316,7 +6316,8 @@ void OBSBasic::OnVirtualCamStart()
 		return;
 
 	vcamButton->setText(QTStr("Basic.Main.StopVirtualCam"));
-	sysTrayVirtualCam->setText(QTStr("Basic.Main.StopVirtualCam"));
+	if (sysTrayVirtualCam)
+		sysTrayVirtualCam->setText(QTStr("Basic.Main.StopVirtualCam"));
 	vcamButton->setChecked(true);
 
 	if (api)
@@ -6333,7 +6334,8 @@ void OBSBasic::OnVirtualCamStop(int)
 		return;
 
 	vcamButton->setText(QTStr("Basic.Main.StartVirtualCam"));
-	sysTrayVirtualCam->setText(QTStr("Basic.Main.StartVirtualCam"));
+	if (sysTrayVirtualCam)
+		sysTrayVirtualCam->setText(QTStr("Basic.Main.StartVirtualCam"));
 	vcamButton->setChecked(false);
 
 	if (api)