Fix cvsimport warning when called without --no-cvs-direct

Perl was warning that $opt_p was undefined in that case.

Signed-off-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>

git-cvsimport.perl

@@ -487,7 +487,7 @@ unless($pid) {
 	my @opt;
 	@opt = split(/,/,$opt_p) if defined $opt_p;
 	unshift @opt, '-z', $opt_z if defined $opt_z;
-	unless ($opt_p =~ m/--no-cvs-direct/) {
+	unless (defined($opt_p) && $opt_p =~ m/--no-cvs-direct/) {
 		push @opt, '--cvs-direct';
 	}
 	exec("cvsps",@opt,"-u","-A",'--root',$opt_d,$cvs_tree);