ObjectToOptionalConverter uses Optional.ofNullable after ConversionSe…

…rvice invocation

Issue: SPR-12589

spring-core/src/main/java/org/springframework/core/convert/support/ObjectToOptionalConverter.java

@@ -69,7 +69,7 @@ public Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor t
 		}
 		else {
 			Object target = this.conversionService.convert(source, sourceType, new GenericTypeDescriptor(targetType));
-			return Optional.of(target);
+			return Optional.ofNullable(target);
 		}
 	}