Fix broken `redirect-rule=` priority parser

Related issue:
- https://github.com/uBlockOrigin/uBlock-issues/issues/1388

Regression from:
- cf2c638d8e

src/js/static-filtering-parser.js

@@ -1169,8 +1169,8 @@ const Parser = class {
         if ( asDataURI ) { token = token.slice(1); }
         const match = /:-?\d+$/.exec(token);
         if ( match !== null ) {
-            token = token.slice(0, match.index);
             priority = parseInt(token.slice(match.index + 1), 10);
+            token = token.slice(0, match.index);
         }
         return { token, priority, asDataURI };
     }