title: The parameter 'custom_events' or 'custom_events_file' is required for the 'CUSTOM_APP_EVENTS' activity
body: <p>Upon upgrading from the Facebook iOS SDK version 3.7.1 to 3.8, I started seeing the following in my console log when authenticating with my app through Facebook:</p>
  
  <pre><code>FBSDKLog: Error Domain=com.facebook.sdk Code=5 "The operation couldn’t be completed. (com.facebook.sdk error 5.)" UserInfo=0xc5a9cf0 {com.facebook.sdk:HTTPStatusCode=400, com.facebook.sdk:ParsedJSONResponseKey={
      body =     {
          error =         {
              code = 100;
              message = "(#100) The parameter 'custom_events' or 'custom_events_file' is required for the 'CUSTOM_APP_EVENTS' activity";
              type = OAuthException;
          };
      };
      code = 400;
      headers =     (
                  {
              name = "Access-Control-Allow-Origin";
              value = "*";
          },
                  {
              name = "Cache-Control";
              value = "no-store";
          },
                  {
              name = Connection;
              value = close;
          },
                  {
              name = "Content-Type";
              value = "text/javascript; charset=UTF-8";
          },
                  {
              name = Expires;
              value = "Sat, 01 Jan 2000 00:00:00 GMT";
          },
                  {
              name = Pragma;
              value = "no-cache";
          },
                  {
              name = "WWW-Authenticate";
              value = "OAuth \"Facebook Platform\" \"invalid_request\" \"(#100) The parameter 'custom_events' or 'custom_events_file' is required for the 'CUSTOM_APP_EVENTS' activity\"";
          },
                  {
              name = "x-fb-loadmon";
              value = "0,2.76,90";
          }
      );
  }, com.facebook.sdk:ErrorSessionKey=&lt;FBSession: 0x12e5e9c0, state: FBSessionStateOpen, loginHandler: 0x12e58630, appID:..., urlSchemeSuffix: , tokenCachingStrategy:&lt;FBSessionTokenCachingStrategy: 0xd884b00&gt;, expirationDate:..., refreshDate:..., attemptedRefreshDate:..., permissions:...&gt;}
  </code></pre>
  
  <p>I've downloaded the most recent versions of the sample Facebook iOS apps and verified that my calls to the Facebook SDK in my AppDelegate are up-to-date. To authenticate, I am sending the <code>openActiveSessionWithReadPermissions:allowLoginUI:completionHandler:</code> message to <code>FBSession</code>.</p>
  
  <p>It seems like this very well could be a Facebook bug (I am going to file a bug with them), but it's also possible that I'm doing something wrong – any help/insights would be appreciated!</p>
  
  <p>I've temporarily resolved the issue by adding a call to <code>[FBAppEvents setFlushBehavior:FBAppEventsFlushBehaviorExplicitOnly];</code> in my AppDelegate, but I would prefer a more comprehensive solution.</p>
  
  <p><strong>3/24/2014 Edit</strong></p>
  
  <p>This no longer repros on 3.8 (nor does it repro on 3.13, which I also tested). Seems like Facebook must have fixed this on the server.</p>