fixed typo to enable/disable -p flag

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@54907 15284696-431f-4ddb-bdfa-cd5b030d7da7

imagery/i.landsat.toar/main.c

@@ -260,7 +260,7 @@ int main(int argc, char *argv[])
     {
         lsat.flag = METADATAFILE;
         lsat_metadata( met, &lsat );
-	if(print_meta) {
+	if(print_meta->answer) {
 		if (lsatmet->answer == NULL) {
 			G_fatal_error(_("Please use a metadata keyword with -p"));
 		}