Don't throw when a user saves account settings without changing their profile

picture.

Summary:
Going to Settings -> Account and hitting "Save" without selecting
a file in the file dialog currently throws.

Test Plan:
Went to Settings -> Account and hit "Save" without making changes.
No exception. Then uploaded a picture normally.

Differential Revision: 30
Reviewed By: tomo
Reviewers: tomo

src/applications/people/controller/settings/PhabricatorUserSettingsController.php

@@ -73,9 +73,12 @@ class PhabricatorUserSettingsController extends PhabricatorPeopleController {
             ->setURI('/settings/page/arcanist/?regenerated=true');
         case 'account':
           if (!empty($_FILES['profile'])) {
+            $err = idx($_FILES['profile'], 'error');
+            if ($err != UPLOAD_ERR_NO_FILE) {
               $file = PhabricatorFile::newFromPHPUpload($_FILES['profile']);
               $user->setProfileImagePHID($file->getPHID());
             }
+          }
 
           $user->save();
           return id(new AphrontRedirectResponse())