SpEL `Indexer` silently ignores failure to set property as index

The `PropertyIndexingValueRef.setValue(Object)` method in SpEL's `Indexer` silently ignores a failure to set a property via the indexing syntax.

For example, if property writes are disabled in the `EvaluationContext`, the SpEL expression `#person['name'] = 'Jane'` evaluates _successfully_ without throwing an exception, but the `name` property is not actually set.
