Bug 842147 - Translate JS exception from CaptivePortalDetector into informative debug message. r=vchang

dom/system/gonk/NetworkManager.js

@@ -868,8 +868,12 @@ let CaptivePortalDetectionHelper = (function() {
       capService.abort(_ongoingInterface);
       _ongoingInterface = null;
     }
-    capService.checkCaptivePortal(interfaceName, capCallback);
-    _ongoingInterface = interfaceName;
+    try {
+      capService.checkCaptivePortal(interfaceName, capCallback);
+      _ongoingInterface = interfaceName;
+    } catch (e) {
+      debug('Fail to detect captive portal due to: ' + e.message);
+    }
   };
 
   let _abort = function (interfaceName) {