Fix .load command failing with 'NoneType object not iterable'

The load_extension() function was missing a return statement. All special
commands must return a list of (title, rows, headers, status) tuples, but
load_extension() returned None implicitly, causing the caller to fail when
iterating over the result.

Fixes #248

Author: daniel7an

litecli/packages/special/dbcommands.py

@@ -254,6 +254,7 @@ def load_extension(cur: DBCursor, arg: str, **_: Any) -> None:
     conn = cur.connection
     conn.enable_load_extension(True)
     conn.load_extension(path)
+    return [(None, None, None, "")]
 
 
 @special_command(