Handle all uerscript errors when hinting with userscript-target

CHANGELOG.asciidoc

@@ -67,6 +67,7 @@ Fixed
 - Worked around a segfault when opening a URL after a QtWebEngine renderer process crash
 - Using :undo or :tab-clone with a view-source:// or chrome:// tab is now prevented, as it segfaults
 - `:navigate prev/next` now detects `rel` attributes on `<a>` elements
+- Fixed a crash when hinting with target `userscript` and spawning a non-existing script
 
 v0.9.1
 ------

qutebrowser/browser/hints.py

@@ -316,7 +316,7 @@ class HintActions:
         try:
             userscripts.run_async(context.tab, cmd, *args, win_id=self._win_id,
                                   env=env)
-        except userscripts.UnsupportedError as e:
+        except userscripts.Error as e:
             raise HintingError(str(e))
 
     def spawn(self, url, context):

tests/end2end/features/hints.feature

@@ -81,6 +81,11 @@ Feature: Using hints
         And I hint with args "all userscript (testdata)/userscripts/echo_hint_text" and follow a
         Then the message "Follow me!" should be shown
 
+    Scenario: Using :hint userscript with a script which doesn't exist
+        When I open data/hints/html/simple.html
+        And I hint with args "all userscript (testdata)/does_not_exist" and follow a
+        Then the error "Userscript '*' not found" should be shown
+
     Scenario: Yanking to clipboard
         When I run :debug-set-fake-clipboard
         And I open data/hints/html/simple.html