Fix mypy errors

I don't think we introduced these, but might as well fix them.

Author: haacked

posthog/client.py

@@ -87,7 +87,10 @@ def get_identity_state(passed) -> tuple[str, bool]:
     return (str(uuid4()), True)
 
 
-def add_context_tags(properties):
+def add_context_tags(properties: Optional[Dict[str, Any]]) -> Dict[str, Any]:
+    if properties is None:
+        properties = {}
+    
     current_context = _get_current_context()
     if current_context:
         context_tags = current_context.collect_tags()
@@ -532,7 +535,7 @@ def capture(
         if personless and "$process_person_profile" not in properties:
             properties["$process_person_profile"] = False
 
-        msg = {
+        msg: Dict[str, Any] = {
             "properties": properties,
             "timestamp": timestamp,
             "distinct_id": distinct_id,