Since g->moffset points to the _maximum_ offset at which the must

Since g->moffset points to the _maximum_ offset at which the must
string may be found (from the beginning of the pattern), the point
at which must is found minus that offset may actually point to some
place before the start of the text.

In that case, make start = start.

Alternatively, this could be tested for in the preceding if, but it
did not occur to me. :-)

Caught by: regex(3) test code