563172 -  migrate_passwd.pl problems with '0' fields

Sent upstream as http://bugzilla.padl.com/show_bug.cgi?id=345

diff -up MigrationTools-47/migrate_passwd.pl.o MigrationTools-47/migrate_passwd.pl
--- MigrationTools-47/migrate_passwd.pl.o	2010-04-27 14:24:54.000000000 +0200
+++ MigrationTools-47/migrate_passwd.pl	2010-04-27 14:25:19.000000000 +0200
@@ -205,22 +205,22 @@ sub dump_shadow_attributes
 	if ($lastchg ne "") {
 		print $HANDLE "shadowLastChange: $lastchg\n";
 	}
-	if ($min) {
+	if ($min ne "") {
 		print $HANDLE "shadowMin: $min\n";
 	}
-	if ($max) {
+	if ($max ne "") {
 		print $HANDLE "shadowMax: $max\n";
 	}
-	if ($warn) {
+	if ($warn ne "") {
 		print $HANDLE "shadowWarning: $warn\n";
 	}
-	if ($inactive) {
+	if ($inactive ne "") {
 		print $HANDLE "shadowInactive: $inactive\n";
 	}
-	if ($expire) {
+	if ($expire ne "") {
 		print $HANDLE "shadowExpire: $expire\n";
 	}
-	if ($flag) {
+	if ($flag ne "") {
 		print $HANDLE "shadowFlag: $flag\n";
 	}
 }