improve wall filter

src/main/java/com/alibaba/druid/sql/ast/statement/SQLDeleteStatement.java

@@ -67,6 +67,9 @@ public class SQLDeleteStatement extends SQLStatementImpl {
     }
 
     public void setWhere(SQLExpr where) {
+        if (where != null) {
+            where.setParent(this);
+        }
         this.where = where;
     }
 

src/main/java/com/alibaba/druid/wall/spi/WallVisitorUtils.java

@@ -241,7 +241,6 @@ public class WallVisitorUtils {
             return;
         }
 
-        x.getWhere().setParent(x);
         checkCondition(visitor, x.getWhere());
         checkConditionForMultiTenant(visitor, x.getWhere(), x);
     }