Decoder: Update check for increment u2_cur_slice_num

Increment u2_cur_slice_num only if current slice had atleast
one MB of memory left.

Test: clusterfuzz generated poc in bug
Bug: b/182152757
Bug: b/179938345
Bug: b/185112718

Change-Id: Ic5eb07e961bccb7fde954bcfd791fd879804e335
(cherry picked from commit a88e0683a420d7ee9aa4b6f41f94cb8dc0c5e040)
1 file changed