Bug 1050000 - check "result" against undefined before use. r=past

toolkit/devtools/webconsole/utils.js

@@ -1177,10 +1177,10 @@ let DebuggerEnvironmentSupport = {
     // TODO: we should use getVariableDescriptor() here - bug 725815.
     let result = aObj.getVariable(aName);
     // FIXME: Need actual UI, bug 941287.
-    if (result.optimizedOut || result.missingArguments) {
+    if (result === undefined || result.optimizedOut || result.missingArguments) {
       return null;
     }
-    return result === undefined ? null : { value: result };
+    return { value: result };
   },
 };