Fix filtering of all hints in number mode

Fixes #1559

qutebrowser/browser/hints.py

@@ -897,7 +897,7 @@ class HintManager(QObject):
             # Whoops, filtered all hints
             modeman.leave(self._win_id, usertypes.KeyMode.hint,
                           'all filtered')
-            return
+            return {}
 
         strings = self._hint_strings(elems)
         self._context.elems = {}

tests/end2end/features/hints.feature

@@ -217,3 +217,13 @@ Feature: Using hints
         And I run :hint all
         And I run :follow-hint 00
         Then data/numbers/1.txt should be loaded
+
+    # https://github.com/The-Compiler/qutebrowser/issues/1559
+    Scenario: Filtering all hints in number mode
+      When I open data/hints/number.html
+      And I set hints -> mode to number
+      And I run :hint all
+      And I press the key "2"
+      And I wait for "Leaving mode KeyMode.hint (reason: all filtered)" in the log
+      Then no crash should happen
+