!834 fix MapToMap ignoreNullValue

Merge pull request !834 from 不忘初心/v5-dev

hutool-core/src/main/java/cn/hutool/core/bean/copier/MapToMapCopier.java

@@ -48,6 +48,10 @@ public class MapToMapCopier extends AbsCopier<Map, Map> {
 			if (false == copyOptions.override && null != targetValue) {
 				return;
 			}
+			// 忽略空值
+			if (true == copyOptions.ignoreNullValue && sValue == null) {
+				return;
+			}
 
 			// 获取目标值真实类型并转换源值
 			final Type[] typeArguments = TypeUtil.getTypeArguments(this.targetType);