Enforce non-null value from getBean and at injection points

Bean-derived null values may still get passed into bean properties and injection points but only if those are declared as non-required. Note that getBean will never return null; a manual bean.equals(null) / "null".equals(bean.toString()) check identifies expected null values now.  This will only ever happen with custom FactoryBeans or factory methods returning null - and since all common cases are handled by autowiring or bean property values in bean definitions, there should be no need to ever manually check for such a null value received from getBean.

Issue: SPR-15829

spring-tx/src/main/java/org/springframework/transaction/support/SimpleTransactionScope.java

@@ -54,7 +54,6 @@ public class SimpleTransactionScope implements Scope {
 		Object scopedObject = scopedObjects.scopedInstances.get(name);
 		if (scopedObject == null) {
 			scopedObject = objectFactory.getObject();
-			Assert.state(scopedObject != null, "Scoped object resolved to null");
 			scopedObjects.scopedInstances.put(name, scopedObject);
 		}
 		return scopedObject;