Fix wrong test in the frustum (missing .length) (#22496)

examples/jsm/csm/Frustum.js

@@ -109,7 +109,7 @@ class Frustum {
 
 			}
 
-			if ( i === breaks - 1 ) {
+			if ( i === breaks.length - 1 ) {
 
 				for ( let j = 0; j < 4; j ++ ) {