Ensure that a window with the given win_id exists

qutebrowser/browser/commands.py

@@ -555,6 +555,10 @@ class CommandDispatcher:
             tabbed_browser = self._new_tabbed_browser(
                 private=self._tabbed_browser.private)
         else:
+            if win_id not in objreg.window_registry:
+                raise cmdexc.CommandError(
+                    "There's no window with id {}!".format(win_id))
+
             tabbed_browser = objreg.get('tabbed-browser', scope='window',
                                         window=win_id)
 

tests/end2end/features/tabs.feature

@@ -1058,6 +1058,11 @@ Feature: Tab management
         And I run :tab-give
         Then the error "Cannot detach from a window with only one tab" should be shown
 
+    Scenario: Give a tab to a window ID that does not exist
+        When I open data/hello.txt
+        And I run :tab-give 99
+        Then the error "There's no window with id 99!" should be shown
+
     # Other
 
     Scenario: Using :tab-next after closing last tab (#1448)