tools/uncoded_frame: fix double free

in case av_interleaved_write_uncoded_frame fails it seems
frame is freed for the second time in fail section.

Signed-off-by: Lukasz Marek <lukasz.m.luki@gmail.com>
Reviewed-by: Nicolas George <george@nsup.org>

This commit also removes 1 trailing whitespace as otherwise the push hook rejects it

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
