Make initial hitBox size match initial width/height

- Otherwise it's possible to have a clickable entity
  with zero size by default which seems like something
  you don't want as a default behavior.

Core/Contents/Source/PolyScreenEntity.cpp

@@ -37,7 +37,7 @@ ScreenEntity::ScreenEntity() : Entity() {
 	color = Color(1.0f,1.0f,1.0f,1.0f);
 	width = 0;
 	height = 0;
-	setHitbox(1, 1);
+	setHitbox(0, 0);
 	backfaceCulled = false;
 	positionMode = POSITION_TOPLEFT;
 	mouseOver = false;