touch: don't compare mouse_touch_events to zero; it's a bool.

src/events/SDL_touch.c

@@ -415,7 +415,7 @@ void SDL_SendTouchMotion(Uint64 timestamp, SDL_TouchID id, SDL_FingerID fingerid
     }
 
     // SDL_HINT_MOUSE_TOUCH_EVENTS: if not set, discard synthetic touch events coming from platform layer
-    if (mouse->mouse_touch_events == 0) {
+    if (!mouse->mouse_touch_events) {
         if (id == SDL_MOUSE_TOUCHID) {
             return;
         }