[bug-gettext] msggrep -f treats empty lines as .*

[Raphaël]

When using msggrep -f file.sed in order to use file.sed as the storage
for a list a regexp (1 per line),
it ignores lines beginning with # but treat empty line as a catch-all (.*)

This is error-prone.

$ cat > a.sed   # no newline
aaaa
^D

$ msggrep -Cf a.sed file.po|wc -l
0       # no match

$ cat > b.sed   # one newline before "aaaa" regexp

aaaa
^D

$ msggrep -Cf b.sed file.po|wc -l
28262   # all lines match