Fix issue 2567: NoneType check before raising exception (#2569)

Co-authored-by: Anuragkillswitch <70265851+Anuragkillswitch@users.noreply.github.com>

redis/connection.py

@@ -340,11 +340,12 @@ def can_read(self, timeout):
         return self._buffer and self._buffer.can_read(timeout)
 
     def read_response(self, disable_decoding=False):
-        pos = self._buffer.get_pos()
+        pos = self._buffer.get_pos() if self._buffer else None
         try:
             result = self._read_response(disable_decoding=disable_decoding)
         except BaseException:
-            self._buffer.rewind(pos)
+            if self._buffer:
+                self._buffer.rewind(pos)
             raise
         else:
             self._buffer.purge()