Fix disabled filter handling in AstFilterChain to match non-chained behavior

The non-chained path in JinjavaInterpreterResolver skips disabled filters
and passes the value through to the next filter. The chained path was
incorrectly returning null for the entire expression, discarding the input
and aborting remaining filters.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: hs-lsong

src/main/java/com/hubspot/jinjava/el/ext/AstFilterChain.java

@@ -85,7 +85,7 @@ public Object eval(Bindings bindings, ELContext context) {
             e
           )
         );
-        return null;
+        continue;
       }
       if (filter == null) {
         interpreter.addError(