Fix custom_field_get_id_from_name() always returning false

Commit 6a7db34 introduced an error in
the call to db_query_bound(), passing the param as a scalar value
instead of an array.

Thanks to user nimmich for noticing the issue and providing a patch.

Fixes #15264

core/custom_field_api.php

@@ -648,7 +648,7 @@ function custom_field_get_id_from_name( $p_field_name, $p_truncated_length = nul
 		$c_field_name = $p_field_name . '%';
 	}
 
-	$t_result = db_query_bound( $query, $c_field_name );
+	$t_result = db_query_bound( $query, array( $c_field_name ) );
 
 	if( db_num_rows( $t_result ) == 0 ) {
 		return false;