don't assert this to ignore empty chunks

Author: leafo

openai/init.lua

@@ -243,7 +243,7 @@ do
             end
             accumulation_buffer = rest
             do
-              chunk = assert(parse_completion_chunk(cjson.decode(json_blob)))
+              chunk = parse_completion_chunk(cjson.decode(json_blob))
               if chunk then
                 chunk_callback(chunk)
               end

openai/init.moon

@@ -253,7 +253,7 @@ class OpenAI
             break
 
           accumulation_buffer = rest
-          if chunk = assert parse_completion_chunk cjson.decode json_blob
+          if chunk = parse_completion_chunk cjson.decode json_blob
             chunk_callback chunk
 
       ...