Fuzzer: Add another stringview subtyping error message to ignore (#6575)

scripts/fuzz_opt.py

diff --git a/scripts/fuzz_opt.py b/scripts/fuzz_opt.py
index 6db2bd3..e91190d 100755
--- a/scripts/fuzz_opt.py
+++ b/scripts/fuzz_opt.py
@@ -671,6 +671,7 @@
             # V8 does not accept nullable stringviews
             # (https://github.com/WebAssembly/binaryen/pull/6574)
             'expected (ref stringview_wtf16), got nullref',
+            'expected type (ref stringview_wtf16), found ref.null of type nullref',
         ]
         for issue in known_issues:
             if issue in output: