Decoder: Handle dec_hdl memory allocation failure gracefully

If memory allocation for dec_hdl fails, return gracefully
with an error code. All other allocation failures are
handled correctly.

Bug: 68300072
Test: ran poc before/after
Change-Id: I118ae71f4aded658441f1932bd4ede3536f5028b
(cherry picked from commit 7720b3fe3de04523da3a9ecec2b42a3748529bbd)