WebGL 2: a small fix to return null for object type.
WebGL 2: a small fix to return null for object type.

Fix errors in object-deletion-behaviour.html in WebGL conformance test.

BUG=295792

Review URL: https://codereview.chromium.org/1281443003

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@200220 bbb929c8-8fbe-4397-9dbb-9b2b20218538

Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk