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

[sbrannen]

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.