Don't allow non-keyboard keys to screenshot/gif in menus

src/m_misc.c

@@ -1531,6 +1531,10 @@ boolean M_ScreenshotResponder(event_t *ev)
 		return false;
 
 	ch = ev->data1;
+
+	if (ch >= KEY_MOUSE1 && menuactive) // If it's not a keyboard key, then don't allow it in the menus!
+		return false;
+
 	if (ch == KEY_F8 || ch == gamecontrol[gc_screenshot][0] || ch == gamecontrol[gc_screenshot][1]) // remappable F8
 		M_ScreenShot();
 	else if (ch == KEY_F9 || ch == gamecontrol[gc_recordgif][0] || ch == gamecontrol[gc_recordgif][1]) // remappable F9