fix(db): pass params=None correctly to both psycopg2 and sqlite3

psycopg2 raises TypeError if params=None is passed to cur.execute()
sqlite3 raises ProgrammingError on unsupported parameter type

db.py

@@ -54,9 +54,14 @@ class DBConn:
         if self.db_type == "postgres":
             import psycopg2.extras
             cur = self._conn.cursor(cursor_factory=psycopg2.extras.RealDictCursor)
+            if params is None:
+                cur.execute(sql)
+            else:
                 cur.execute(sql, params)
             return cur
         else:
+            if params is None:
+                return self._conn.execute(sql)
             return self._conn.execute(sql, params)
 
     def executemany(self, sql: str, seq):