Handle a mergedBy NaN value

This avoids a TypeError when retrieving PRs that have not been merged, which was causing a critical error. From where mergedBy is set, it can be a pandas na or it can be a username.

Fixes #164

Author: jasongrout

github_activity/github_activity.py

@@ -550,7 +550,7 @@ def filter_ignored(userlist):
                 item_contributors.add(committer)
             # Only add merger if they're not a bot and not the author
             if (
-                row.mergedBy
+                pd.notna(row.mergedBy)
                 and row.mergedBy != row.author
                 and not ignored_user(row.mergedBy)
             ):

github_activity/graphql.py

@@ -323,7 +323,7 @@ def is_bot(user_dict):
 
         # Add some extra fields
         def get_login(user):
-            return user["login"] if not pd.isna(user) else user
+            return user["login"] if pd.notna(user) else user
 
         self.data["author"] = self.data["author"].map(get_login)
         self.data["mergedBy"] = self.data["mergedBy"].map(get_login)