[clang-format] git-clang-format throws an assertion when removing files as part of the commit

Following a change {D111273} to allow git-clang-format to see single lines being removed,
we introduced a regression such that if you are removing a whole file it will
assert in clang-format as its given the -lines=0:0  (lines are 1 based)

Reviewed By: HazardyKnusperkeks

Differential Revision: https://reviews.llvm.org/D112056