Fix issue with pack_commands returning an empty byte sequence

Author: jmcbailey

redis/asyncio/connection.py

@@ -975,7 +975,8 @@ def pack_commands(self, commands: Iterable[Iterable[EncodableT]]) -> List[bytes]
                     or chunklen > buffer_cutoff
                     or isinstance(chunk, memoryview)
                 ):
-                    output.append(SYM_EMPTY.join(pieces))
+                    if pieces:
+                        output.append(SYM_EMPTY.join(pieces))
                     buffer_length = 0
                     pieces = []
 

redis/connection.py

@@ -875,7 +875,8 @@ def pack_commands(self, commands):
                     or chunklen > buffer_cutoff
                     or isinstance(chunk, memoryview)
                 ):
-                    output.append(SYM_EMPTY.join(pieces))
+                    if pieces:
+                        output.append(SYM_EMPTY.join(pieces))
                     buffer_length = 0
                     pieces = []