Fix a number of warnings

Structures with anonymous unions would a warning when you do a brace
assignment on them.

Also fixed some unused parameters and removed some unused variables.

obs/window-basic-transform.cpp

@@ -14,6 +14,7 @@ static OBSSceneItem FindASelectedItem(OBSScene scene)
 			return false;
 		}
 
+		UNUSED_PARAMETER(scene);
 		return true;
 	};