Repair so error on npm -ls becomes a warning

* Added `try...catch` just in case it's a fatal error

**NOTES**

``` sh-session
problems": [

    "peer dep missing: kerberos@~0.0, required by mongodb-core@1.2.21"

],
```

... this shows up in the stdout as being the "error" along with the full compliment of packages installed ... see OpenUserJS#832 and parent OpenUserJS#318

*(never would have guessed this on nodejitsu... glad we aren't there anymore)*

controllers/admin.js

@@ -337,11 +337,14 @@ exports.adminNpmListView = function (aReq, aRes, aNext) {
 
   exec('npm ls --json', function (aErr, aStdout, aStderr) {
     if (aErr) {
-      aRes.status(501).send({ status: 501, message: 'Not implemented.' });
-      return;
+      console.warn(aErr);
     }
 
-    aRes.json(JSON.parse(aStdout));
+    try {
+      aRes.json(JSON.parse(aStdout));
+    } catch (aE) {
+      aRes.status(520).send({ status: 520, message: 'Unknown error.' });
+    }
   });
 };