PixelationPassNode: Fix zero normal processing. (#32159)

examples/jsm/tsl/display/PixelationPassNode.js

@@ -193,7 +193,7 @@ class PixelationNode extends TempNode {
 
 			const nei = property( 'float', 'nei' );
 
-			If( this.normalEdgeStrength.greaterThan( 0.0 ), () => {
+			If( this.normalEdgeStrength.greaterThan( 0.0 ).and( normal.length().greaterThan( 0 ) ), () => {
 
 				nei.assign( normalEdgeIndicator( depth, normal ) );