version.sh: fix empty result when git describe fails

fixes an error in travis, which makes a shallow clone of 50 commits.
if the last tag is older than 50 commits, we get:
"fatal: No names found, cannot describe anything."

this caused a premature exit due to an assert error in safe_write()
on this line: assert (count > 0);

because the version variable in tinyproxy was empty.

0 files changed, 0 insertions, 0 deletions