LibWeb: Propogate OOM errors from readable_stream_reader_generic_cancel

Author: https://github.com/mattco98
Commit: db1be40b13
Pull-request: https://github.com/SerenityOS/serenity/pull/18297
Reviewed-by: https://github.com/linusg

Userland/Libraries/LibWeb/Streams/ReadableStreamGenericReader.cpp

@@ -32,7 +32,7 @@ WebIDL::ExceptionOr<JS::NonnullGCPtr<JS::Promise>> ReadableStreamGenericReaderMi
     }
 
     // 2. Return ! ReadableStreamReaderGenericCancel(this, reason).
-    auto promise_capability = readable_stream_reader_generic_cancel(*this, reason);
+    auto promise_capability = TRY(readable_stream_reader_generic_cancel(*this, reason));
     return JS::NonnullGCPtr { verify_cast<JS::Promise>(*promise_capability->promise().ptr()) };
 }