Allow empty defsearch.

common/content/completion.js

@@ -1645,7 +1645,7 @@ function Completion() //{{{
             let engines = bookmarks.getSearchEngines();
 
             context.title = ["Search Keywords"];
-            context.completions = keywords.concat(engines);
+            context.completions = [ bookmarks.makeKeyword("", "No default search engine", null, "") ].concat( keywords.concat(engines) );
             context.keys = { text: 0, description: 1, icon: 2 };
 
             if (!space || noSuggest)

vimperator/content/bookmarks.js

@@ -589,6 +589,13 @@ function Bookmarks() //{{{
                 return process(resp);
         },
 
+        // Allows for creation of anonymous keyword (e.g., for empty
+        // defsearch's)
+        makeKeyword: function makeKeyword(keyword, title, icon, url)
+        {
+            return new Keyword( keyword, title, icon, url );
+        },
+
         // TODO: add filtering
         // format of returned array:
         // [keyword, helptext, url]

vimperator/locale/en-US/options.txt

@@ -247,6 +247,9 @@ This means, it you set 'defsearch' to "youtube", then [c]:open arnold
 schwarzenegger[c] will be exactly the same as [c]:open youtube arnold
 schwarzenegger[c]. Therefore, you need to add a keyword or search engine
 "youtube" first.
+
+If 'defsearch' is empty, then Firefox will always attempt to open the
+raw [[arg]].
 ____