fix: fix for case when value is none

Author: jackrua

pgvector/sqlalchemy/bit.py

@@ -26,8 +26,10 @@ def process(value):
 
     def result_processor(self, dialect, coltype):
         def process(value): 
-            if value and isinstance(dialect, PGDialect_asyncpg):
-                return value.as_string()
+            if value is None: return None
+            else: 
+                if isinstance(dialect, PGDialect_asyncpg): 
+                    return value.as_string()
             return Bit._from_db(value).to_text() 
         return process