Refine embeddable emptiness checks to consider whether the collection holds entities.

Embedded entities which contain a empty collection of values that aren't entities are now considered empty, if this collection is empty.

Closes #1737
Original pull request: #1812

spring-data-jdbc/src/main/java/org/springframework/data/jdbc/core/convert/MappingJdbcConverter.java

@@ -422,7 +422,7 @@ public class MappingJdbcConverter extends MappingRelationalConverter implements
 		@Override
 		public boolean hasValue(RelationalPersistentProperty property) {
 
-			if (property.isCollectionLike() || property.isMap()) {
+			if ((property.isCollectionLike() && property.isEntity())|| property.isMap()) {
 				// attempt relation fetch
 				return true;
 			}