[GEN] Backport bug fixes in CWorldBuilderDoc::OnNewDocument from Zero Hour (#1099)

Author: Caball009

Generals/Code/Tools/WorldBuilder/src/WorldBuilderDoc.cpp

@@ -1210,7 +1210,16 @@ BOOL CWorldBuilderDoc::OnNewDocument()
 	m_waypointTableNeedsUpdate = true;
 	m_curWaypointID = 0;
 	WbApp()->selectPointerTool();
+
+	// Make sure that all the old units are removed from the list.
+	// Bug fix by MLL 1/14/03
+	TheLayersList->enableUpdates();
+	TheLayersList->resetLayers();
+	TheLayersList->disableUpdates();
+
+	// TheSuperHackers @bugfix Caball009 20/06/2025 Must not delete polygon triggers before calling enableUpdates.
 	PolygonTrigger::deleteTriggers();
+
 	TheSidesList->clear();
 	TheSidesList->validateSides();