Ensure that origin field in the packing list structure is initialised. This

fixes problem when there are origin-less packages installed on a system

Reported by:	Mark Knight <markk@knigma.org>
MFC after:	3 days

usr.sbin/pkg_install/lib/plist.c

@@ -260,6 +260,7 @@ read_plist(Package *pkg, FILE *fp)
 
     pkg->fmtver_maj = 1;
     pkg->fmtver_mnr = 0;
+    pkg->origin = NULL;
     while (fgets(pline, FILENAME_MAX, fp)) {
 	int len = strlen(pline);