fix clear

mybatis-plus-core/src/main/java/com/baomidou/mybatisplus/core/conditions/query/LambdaQueryWrapper.java

@@ -132,6 +132,6 @@ public class LambdaQueryWrapper<T> extends AbstractLambdaWrapper<T, LambdaQueryW
     @Override
     public void clear() {
         super.clear();
-        sqlSelect.clear();
+        sqlSelect.setStringValue(null);
     }
 }

mybatis-plus-core/src/main/java/com/baomidou/mybatisplus/core/conditions/query/QueryWrapper.java

@@ -118,6 +118,6 @@ public class QueryWrapper<T> extends AbstractWrapper<T, String, QueryWrapper<T>>
     @Override
     public void clear() {
         super.clear();
-        sqlSelect.clear();
+        sqlSelect.setStringValue(null);
     }
 }

mybatis-plus-extension/src/main/kotlin/com/baomidou/mybatisplus/extension/kotlin/KtQueryWrapper.kt

@@ -116,6 +116,6 @@ class KtQueryWrapper<T : Any> : AbstractKtWrapper<T, KtQueryWrapper<T>>, Query<K
 
     override fun clear() {
         super.clear()
-        sqlSelect.clear()
+        sqlSelect.stringValue = null
     }
 }