[examples] clang-tidy in use_media_decoder

A local variable is set in all paths that don't exit(). However,
clang-tidy doesn't appear to interpret this appropriately, so now
we pre-initialize that local var.

This moves garnet/examples/media/ to a state of 0 clang-tidy warnings.

Test: build, CQ, "git-file-tidy --all" is clean in examples/media

Change-Id: Ib9e49d2631de439f540dade8688eee7dc432296f
1 file changed