Chrome extension throwing error in console

Question

My content script sends a message to background.js. In the callback handler for response, I had the last line as "alert(alrt_msg)". Upon executing code, I get the alert box, but after clicking "OK", the chrome console shows following in red:

Error in event handler for 'undefined': Cannot call method 'disconnect' of null TypeError: Cannot call method 'disconnect' of null
    at chromeHidden.Port.sendMessageImpl (miscellaneous_bindings:285:14)
    at chrome.Event.dispatch (event_bindings:237:41)
    at Object.chromeHidden.Port.dispatchOnMessage (miscellaneous_bindings:250:22) 

Its not much informative but intuitively I knew that this error is because some structure somewhere is garbage collected while user clicks on "OK". So I put my code as

window.setTimeout(function() { alert(alrt_msg); } , 1);

This made it work without above error. Still, after searching for documentation or google, I was not able to find the exact reason behind this. Can someone please explain whats going on and if documentation contains a specific way to do this?

Answer 1

I have came to the same issue. This is due to an error (my code's fault) in a function which is called in the response handler.

Here is my code:

In background.js - the listening side

chrome.runtime.onMessage.addListener(
  function(request, sender, sendResponse) {
    var update_msg = 'test';
    sendResponse({data: update_msg});
    return false; // -> Add this or not add this do not matter
  });
}

On the sending side:

function updateObjDatabase(obj) {
  chrome.runtime.sendMessage({data: obj}, function(response) {
    // Update when it's done
    update_msg_handler(response.data);
  });
}

function update_msg_handler(msg) {
  ..... error code here
}

The wrong code is actually in the function update_msg_handler. But the Chrome console just won't tell you that details. You have to add some console.log to debug if you don't have an IDE.

Answer 2

I had same error. It was iMacros app. After I deleted it no error.