fix #3287

src/js/tab.js

@@ -547,18 +547,21 @@ vAPI.tabs.onPopupUpdated = (function() {
         logData;
 
     // https://github.com/gorhill/uBlock/commit/1d448b85b2931412508aa01bf899e0b6f0033626#commitcomment-14944764
-    // See if two URLs are different, disregarding scheme -- because the scheme
-    // can be unilaterally changed by the browser.
+    //   See if two URLs are different, disregarding scheme -- because the
+    //   scheme can be unilaterally changed by the browser.
+    // https://github.com/gorhill/uBlock/issues/1378
+    //   Maybe no link element was clicked.
     var areDifferentURLs = function(a, b) {
-        // https://github.com/gorhill/uBlock/issues/1378
-        // Maybe no link element was clicked.
         if ( b === '' ) { return true; }
+        if ( b.startsWith('about:') ) { return false; }
         var pos = a.indexOf('://');
         if ( pos === -1 ) { return false; }
         a = a.slice(pos);
         pos = b.indexOf('://');
-        if ( pos === -1 ) { return false; }
-        return b.slice(pos) !== a;
+        if ( pos !== -1 ) {
+            b = b.slice(pos);
+        }
+        return b !== a;
     };
 
     var popupMatch = function(openerURL, targetURL, popupType) {