libgui: Propagate error by clearing sp<GB>

Clears the sp<GraphicBuffer> returned by createGraphicBuffer when there
is an error during unflattening.

Bug: 21498231
Change-Id: I886da4474fc06853cc59188d62044b7d7549126b
(cherry picked from commit 6a04e5fcf67e754b215301fe38a6401db567f4b5)
1 file changed