Dupe Glitch (all snapshots from 14w11b)

this bug happends when you (only tested on east direction) place a 3 block construction with a comparator sticking out and then a item frame with a item in it
before: http://puu.sh/9f26i.png after: http://puu.sh/9f28E.png

i also tested it with a other entity just under the "corrupted" tile/entity:
and this before: http://puu.sh/9f2zA.jpg after: http://puu.sh/9f2Bm.jpg