Handle empty command in CommandRunner.parse_all

Sicne we now call self._get_alias there, we also need to make sure it's
not an empty string before that.

Introduced in #1577. Fixes #1690.

qutebrowser/commands/runners.py

@@ -119,6 +119,9 @@ class CommandRunner(QObject):
         Yields:
             ParseResult tuples.
         """
+        if not text:
+            raise cmdexc.NoSuchCommandError("No command given")
+
         if aliases:
             text = self._get_alias(text, text)
 

tests/unit/commands/test_runners.py

@@ -53,6 +53,15 @@ class TestCommandRunner:
             with pytest.raises(cmdexc.NoSuchCommandError):
                 list(cr.parse_all("alias_name"))
 
+    def test_parse_empty_with_alias(self):
+        """An empty command should not crash.
+
+        See https://github.com/The-Compiler/qutebrowser/issues/1690
+        """
+        cr = runners.CommandRunner(0)
+        with pytest.raises(cmdexc.NoSuchCommandError):
+            list(cr.parse_all(''))
+
     def test_parse_with_count(self):
         """Test parsing of commands with a count."""
         cr = runners.CommandRunner(0)