Fix data format convert problem for PostgreSQL graph storage

lightrag/kg/postgres_impl.py

@@ -1100,11 +1100,14 @@ class PGGraphStorage(BaseGraphStorage):
                     elif dtype == "edge":
                         d[k] = json.loads(v)
             else:
-                d[k] = (
-                    json.loads(v)
-                    if isinstance(v, str) and ("{" in v or "[" in v)
-                    else v
-                )
+                try:
+                    d[k] = (
+                        json.loads(v)
+                        if isinstance(v, str) and (v.startswith("{") or v.startswith("["))
+                        else v
+                    )
+                except json.JSONDecodeError:
+                    d[k] = v
 
         return d