Remove PARENT_TOP and PARENT_LEFT from integer expressions for widgets

PARENT_TOP and PARENT_LEFT should be 0 so they are not very useful substitutions. They are replaced with 0 or removed if that was the whole value for a field.

OpenRA.Mods.Common/UpdateRules/UpdatePath.cs

@@ -90,6 +90,7 @@ namespace OpenRA.Mods.Common.UpdateRules
 				new AddSupportPowerBlockedCursor(),
 				new MovePreviewFacing(),
 				new RenameOnDeath(),
+				new RemoveParentTopParentLeftSubstitutions(),
 
 				// Execute these rules last to avoid premature yaml merge crashes.
 				new ReplaceCloakPalette(),