[inspector] fixed injected-script-host crash

src/inspector/injected-script-source.js

 /*
  * Copyright (C) 2007 Apple Inc.  All rights reserved.
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
@@ skipping 385 matching lines @@
                     name = /** @type {string} */ (injectedScript._describe(property));
                 else
                     name = typeof property === "number" ? ("" + property) : /** @type {string} */(property);
 
                 if (subtype === "internal#scopeList" && name === "length")
                     continue;
 
                 var descriptor;
                 try {
                     descriptor = InjectedScriptHost.getOwnPropertyDescriptor(o, property);
-                    InjectedScriptHost.nullifyPrototype(descriptor);
+                    if (descriptor) {
+                        InjectedScriptHost.nullifyPrototype(descriptor);
+                    }
                     var isAccessorProperty = descriptor && ("get" in descriptor || "set" in descriptor);
                     if (accessorPropertiesOnly && !isAccessorProperty)
                         continue;
                     if (descriptor && "get" in descriptor && "set" in descriptor && name !== "__proto__" &&
                             InjectedScriptHost.formatAccessorsAsProperties(object, descriptor.get) &&
                             !doesAttributeHaveObservableSideEffectOnGet(object, name)) {
                         descriptor.value = object[property];
                         descriptor.isOwn = true;
                         delete descriptor.get;
                         delete descriptor.set;
@@ skipping 648 matching lines @@
             return string.substr(0, leftHalf) + "\u2026" + string.substr(string.length - rightHalf, rightHalf);
         }
         return string.substr(0, maxLength) + "\u2026";
     },
 
     __proto__: null
 }
 
 return injectedScript;
 })