[PATCH] gitweb.cgi: Create $git_temp if it doesn't exist

Unless we'd done diffs, $git_temp doesn't exist and then
mime lookups fail.  Explicitly create it, if it doesn't
exist already.

Signed-off-by: Luben Tuikov <redacted>
---
 gitweb/gitweb.cgi |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)