Camera: Wrong count is displayed when view details for a video

mSource size is coming as 2 even if there is only one image due to
wrong initialization. Fixing that initializaiton may break other use cases.
So, the fix has been given only for this particular error (Wrong count).

Change-Id: I65117dd34d2ec80ca68e5a22e0403f5470e2621a
CRs-fixed: 514328