Re-add null check for closure-data (Originally removed in 177dee8f1621eef43d5c820f1a0e9d91bce1dc6d)

pkg/compiler/lib/src/js_emitter/runtime_type_generator.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of dart2js.js_emitter;
 
 // Function signatures used in the generation of runtime type information.
 typedef void FunctionTypeSignatureEmitter(
     Element method, FunctionType methodType);
 
@@ skipping 63 matching lines @@
       }
     }
 
     void generateFunctionTypeSignature(
         FunctionElement method, FunctionType type) {
       assert(method.isImplementation);
       jsAst.Expression thisAccess = new jsAst.This();
       if (!method.isAbstract) {
         ClosureClassMap closureData = compiler.closureToClassMapper
             .getClosureToClassMapping(method.resolvedAst);
-        ClosureFieldElement thisLocal =
-            closureData.freeVariableMap[closureData.thisLocal];
-        if (thisLocal != null) {
-          jsAst.Name thisName = namer.instanceFieldPropertyName(thisLocal);
-          thisAccess = js('this.#', thisName);
+        if (closureData != null) {
+          ClosureFieldElement thisLocal =
+              closureData.freeVariableMap[closureData.thisLocal];
+          if (thisLocal != null) {
+            jsAst.Name thisName = namer.instanceFieldPropertyName(thisLocal);
+            thisAccess = js('this.#', thisName);
+          }
         }
       }
 
       if (storeFunctionTypeInMetadata && !type.containsTypeVariables) {
         result.functionTypeIndex =
             emitterTask.metadataCollector.reifyType(type);
       } else {
         RuntimeTypesEncoder rtiEncoder = backend.rtiEncoder;
         jsAst.Expression encoding =
             rtiEncoder.getSignatureEncoding(type, thisAccess);
@@ skipping 234 matching lines @@
     }
     jsAst.Expression convertRtiToRuntimeType = backend.emitter
         .staticFunctionAccess(backend.helpers.convertRtiToRuntimeType);
 
     return new StubMethod(
         name,
         js('function () { return #(#) }',
             [convertRtiToRuntimeType, computeTypeVariable]));
   }
 }