Allow :open without URL with -t/-b/-w

CHANGELOG.asciidoc

@@ -150,6 +150,7 @@ Changed
 - `:hint` has a new `--add-history` argument to add the URL to the history for
   yank/spawn targets.
 - `:set` now cycles through values if more than one argument is given.
+- `:open` now opens `default-page` without an URL even without `-t`/`-b`/`-w` given.
 
 Deprecated
 ~~~~~~~~~~

qutebrowser/browser/commands.py

@@ -257,13 +257,10 @@ class CommandDispatcher:
             count: The tab index to open the URL in, or None.
         """
         if url is None:
-            if tab or bg or window:
+            urls = [config.get('general', 'default-page')]
-                urls = [config.get('general', 'default-page')]
-            else:
-                raise cmdexc.CommandError("No URL given, but -t/-b/-w is not "
-                                          "set!")
         else:
             urls = self._parse_url_input(url)
+
         for i, cur_url in enumerate(urls):
             if not window and i > 0:
                 tab = False

tests/end2end/features/open.feature

@@ -14,9 +14,10 @@ Feature: Opening pages
                 - active: true
                   url: http://localhost:*/data/numbers/1.txt
 
-    Scenario: :open without URL and no -t/-b/-w
+    Scenario: :open without URL
-        When I run :open
+        When I set general -> default-page to http://localhost:(port)/data/numbers/11.txt
-        Then the error "No URL given, but -t/-b/-w is not set!" should be shown
+        And I run :open
+        Then data/numbers/11.txt should be loaded
 
     Scenario: :open without URL and -t
         When I set general -> default-page to http://localhost:(port)/data/numbers/2.txt