bitbake: hashserv: client: Fix handling of null responses

If the server returns an empty response ("null" in json), this cannot
be iterated to check for the presence of the "chunk-stream" key.

(Bitbake rev: bf75370bcd6d02ed08cd959eec6190196b792515)

Signed-off-by: Paul Barker <pbarker@konsulko.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/hashserv/client.py

@@ -99,7 +99,7 @@ class AsyncClient(object):
             l = await get_line()
 
             m = json.loads(l)
-            if "chunk-stream" in m:
+            if m and "chunk-stream" in m:
                 lines = []
                 while True:
                     l = (await get_line()).rstrip("\n")