Fix multiline output export-v2

Author: mnoszczak

libs/labelbox/src/labelbox/schema/export_task.py

@@ -584,8 +584,10 @@ def errors(self):
                          metadata_header),
             _MultiGCSFileReader(),
             JsonConverter(),
-        ).start(stream_handler=lambda output: data.append(
-            json.loads(output.json_str)))
+        ).start(stream_handler=lambda output: [
+            data.append(json.loads(row)) for row in output.json_str.split(
+                '\n') if row
+        ])
         return data
 
     @property