fix NPE in TopScopeObject

Author: wirthi

graal-js/src/com.oracle.truffle.js/src/com/oracle/truffle/js/runtime/interop/TopScopeObject.java

@@ -266,7 +266,7 @@ boolean isMemberRemovable(String member,
     void removeMember(String member,
                     @Shared("interop") @CachedLibrary(limit = "LIMIT") InteropLibrary interop) throws UnsupportedMessageException, UnknownIdentifierException {
         int length = NAMES.length;
-        for (int i = 0; i < length; i++) {
+        for (int i = scopeIndex; i < length; i++) {
             Object scope = this.objects[i];
             if (interop.isMemberRemovable(scope, member)) {
                 interop.removeMember(scope, member);