Fix picks on clipped regions

CHANGES.md

@@ -13,6 +13,7 @@
 
 - Removes the minimum tile threshold of four for WMTS. [#4372](https://github.com/CesiumGS/cesium/issues/4372)
 - Fixed a crash that could happen when loading PNTS (point cloud) data that contained a batch table without a binary part [#11166](https://github.com/CesiumGS/cesium/issues/11166)
+- Fixed an error picking an area hidden by a `ClippingPolygon`. [#12725](https://github.com/CesiumGS/cesium/issues/12725)
 
 #### Additions :tada:
 

packages/engine/Source/Scene/Model/ModelClippingPolygonsPipelineStage.js

@@ -79,10 +79,14 @@ ModelClippingPolygonsPipelineStage.process = function (
 
   const uniformMap = {
     model_clippingDistance: function () {
-      return clippingPolygons.clippingTexture;
+      return (
+        clippingPolygons.clippingTexture ?? frameState.context.defaultTexture
+      );
     },
     model_clippingExtents: function () {
-      return clippingPolygons.extentsTexture;
+      return (
+        clippingPolygons.extentsTexture ?? frameState.context.defaultTexture
+      );
     },
   };