Fixed JSON.stringify() and njs.dump() allocation error handling.
Fixed JSON.stringify() and njs.dump() allocation error handling.

Previously, the return value of njs_json_buf_append() was not
verified in some places.

Found by Coverity (CID 1456031).

nginx/njs,nginx/njs,nginx/njs,nginx/njs,nginx/njs,nginx/njs