Fix error dispatching fullscreen autocmd again.

common/content/autocommands.js

@@ -143,7 +143,7 @@ var AutoCommands = Module("autocommands", {
         let lastPattern = null;
         var { url, doc } = args;
         if (url)
-            uri = util.newURI(url);
+            uri = util.createURI(url);
         else
             var { uri, doc } = buffer;
 

common/modules/util.jsm

@@ -964,7 +964,7 @@ var Util = Module("Util", XPCOM([Ci.nsIObserver, Ci.nsISupportsWeakReference]),
      * @returns {nsIURI}
      */
     // FIXME: createURI needed too?
-    newURI: function (uri, charset, base) services.io.newURI(uri, charset, base),
+    newURI: function newURI(uri, charset, base) this.withProperErrors("newURI", services.io, uri, charset, base),
 
     /**
      * Removes leading garbage prepended to URIs by the subscript
@@ -1765,6 +1765,23 @@ var Util = Module("Util", XPCOM([Ci.nsIObserver, Ci.nsISupportsWeakReference]),
         return res.filter(function (h) !set.add(seen, h.spec));
     },
 
+    /**
+     * Wraps native exceptions thrown by the called function so that a
+     * proper stack trace may be retrieved from them.
+     *
+     * @param {function|string} meth The method to call.
+     * @param {object} self The 'this' object of the method.
+     * @param ... Arguments to pass to *meth*.
+     */
+    withProperErrors: function withProperErrors(meth, self) {
+        try {
+            return (callable(meth) ? meth : self[meth]).apply(self, Array.slice(arguments, withProperErrors.length));
+        }
+        catch (e) {
+            throw e.stack ? e : Error(e);
+        }
+    },
+
     /**
      * Converts an E4X XML literal to a DOM node. Any attribute named
      * highlight is present, it is transformed into dactyl:highlight,