fix(tools): avoid using undef resize args when getting server screenshot

tools/anvil-get-server-screenshot

@@ -49,12 +49,14 @@ sub get_server_screenshot
 {
 	my $parameters  = shift;
 	my $server_uuid = $parameters->{server_uuid};
-	my ($resize_x, $resize_y) = split(/x/ , $parameters->{resize_args});
+	my $resize_args = defined $parameters->{resize_args} ? $parameters->{resize_args} : '';
 
 	my $shell_call = "virsh --quiet screenshot --domain ".$server_uuid." --file /dev/stdout";
 
-	if ($resize_x =~ /^\d+$/ && $resize_y =~ /^\d+$/)
+	if ($resize_args =~ /^\d+x\d+$/)
 	{
+		my ($resize_x, $resize_y) = split(/x/ , $resize_args);
+
 		$shell_call .= " | pamscale -quiet -xyfit ".$resize_x." ".$resize_y;
 	}