Fix deletion of default category on MSSQL/Oracle

$f_category_id is of type int, but the config table's config_id column
is defined as VARCHAR(64). This causes a type mismatch on some RDBMS:

- Oracle (ORA-00932: inconsistent data types: expected -, found CLOB)
- MSSQL

Problem resolved by casting the variable to string when passing it to
db_query().

Fixes #16384

manage_proj_cat_delete.php

@@ -68,7 +68,7 @@
 # Protect the 'default category for moves' from deletion
 $t_default_category_id = config_get( 'default_category_for_moves', /* default */ null, ALL_USERS, ALL_PROJECTS );
 $t_query = 'SELECT count(config_id) FROM {config} WHERE config_id = ' . db_param() . ' AND value = ' . db_param();
-$t_default_cat_count = db_result( db_query( $t_query, array( 'default_category_for_moves', $f_category_id ) ) );
+$t_default_cat_count = db_result( db_query( $t_query, array( 'default_category_for_moves', (string)$f_category_id ) ) );
 if( $t_default_cat_count > 0 || $f_category_id == $t_default_category_id ) {
 	trigger_error( ERROR_CATEGORY_CANNOT_DELETE_DEFAULT, ERROR );
 }