Fix :bookmark-add with no URL

doc/changelog.asciidoc

@@ -51,6 +51,8 @@ Fixed
 - QtWebKit: `:view-source` now displays a valid URL.
 - URLs containing ampersands and other special chars are now shown
   correctly when filtering them in the completion.
+- `:bookmark-add "" foo` can now be used to save the current URL with a custom
+  title.
 
 v1.1.1
 ------

doc/help/commands.asciidoc

@@ -176,7 +176,8 @@ Save the current page as a bookmark, or a specific url.
 If no url and title are provided, then save the current page as a bookmark. If a url and title have been provided, then save the given url as a bookmark with the provided title. You can view all saved bookmarks on the link:qute://bookmarks[bookmarks page].
 
 ==== positional arguments
-* +'url'+: url to save as a bookmark. If None, use url of current page.
+* +'url'+: url to save as a bookmark. If not given, use url of current page.
+
 * +'title'+: title of the new bookmark.
 
 ==== optional arguments

qutebrowser/browser/commands.py

@@ -1349,7 +1349,8 @@ class CommandDispatcher:
         link:qute://bookmarks[bookmarks page].
 
         Args:
-            url: url to save as a bookmark. If None, use url of current page.
+            url: url to save as a bookmark. If not given, use url of current
+                 page.
             title: title of the new bookmark.
             toggle: remove the bookmark instead of raising an error if it
                     already exists.
@@ -1358,7 +1359,7 @@ class CommandDispatcher:
             raise cmdexc.CommandError('Title must be provided if url has '
                                       'been provided')
         bookmark_manager = objreg.get('bookmark-manager')
-        if url is None:
+        if not url:
             url = self._current_url()
         else:
             try: