patch(1): don't assume a match if we run out of context to check

Patches with very little context (-U0 and -U1) could get misapplied if
the file to be patched changes and a hunk is no longer applicable. Matching
with fuzz would be attempted and default to a match when we unexpectedly ran
out of context.

PR: 74127
Reviewed by: emaste, pfg
Approved by: emaste (mentor)
Differential Revision: https://reviews.freebsd.org/D12631