Merge pull request #1646 from DawnKing/master

index is not set, it's always undefined.

src/Cameras/babylon.camera.ts

@@ -353,6 +353,7 @@
                         result.push(i);
                         continue;
                     }
+                    index = atIndices[i];
                     this._postProcesses.splice(index, 1);
                 }
             }