Merge pull request #3738 from Inighty/3.0

wrapper clear 将sqlSegment重置为空串 缓存标志重置为true

mybatis-plus-core/src/main/java/com/baomidou/mybatisplus/core/conditions/segments/MergeSegments.java

@@ -80,6 +80,8 @@ public class MergeSegments implements ISqlSegment {
      * @since 3.3.1
      */
     public void clear() {
+        sqlSegment = StringPool.EMPTY;
+        cacheSqlSegment = true;
         normal.clear();
         groupBy.clear();
         having.clear();