gitweb: esc_html_hl_regions(): Don't create empty <span> elements
gitweb: esc_html_hl_regions(): Don't create empty <span> elements

If $end is equal to or less than $begin, esc_html_hl_regions()
generates an empty <span> element.  It normally shouldn't be visible in
the web browser, but it doesn't look good when looking at page source.
It also minimally increases generated page size for no special reason.

Signed-off-by: Michał Kiedrowicz <3303283adeb04caefcc13da64be4ce1c6c137c62@gmail.com>
Acked-by: Jakub Narębski <a6a1517a087f9f64a72f41a0de57ff01fbb0e412@gmail.com>
Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git