[Case 6491] makeStretchTool: Fix z undefined issue (details below).

z:z appears to have been a typo, as there's no var z.  Should likely be z:1.

Changes Committed:
	modified:   scripts/system/libraries/entitySelectionTool.js

scripts/system/libraries/entitySelectionTool.js

@@ -2833,7 +2833,7 @@ SelectionDisplay = (function() {
                     planeNormal = {
                         x: 0,
                         y: 0,
-                        z: z
+                        z: 1
                     };
                 }
             }