Diskmanage: correctly add wearout value of 0

if wearout is 0 we showed 'N/A' instead of 100%
(wearout is really the 'life left' value)

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>

PVE/Diskmanage.pm

@@ -512,7 +512,7 @@ sub get_disks {
 		if ($type eq 'ssd') {
 		    # if we have an ssd we try to get the wearout indicator
 		    my $wearval = get_wear_leveling_info($smartdata, $data->{model} || $sysdata->{model});
-		    $wearout = $wearval if $wearval;
+		    $wearout = $wearval if defined($wearval);
 		}
 	    };
 	}