Pick sqlite upstream patch from
https://github.com/sqlite/sqlite/commit/75e95e1fcd52d3ec8282edb75ac8cd0814095d54
to fix CVE-2019-19880.
diff --git a/sqlite3.c b/sqlite3.c
index 8fd740b..1a5886b 100644
--- a/sqlite3.c
+++ b/sqlite3.c
@@ -147583,9 +147583,11 @@ static ExprList *exprListAppendList(
     int nInit = pList ? pList->nExpr : 0;
     for(i=0; i<pAppend->nExpr; i++){
       Expr *pDup = sqlite3ExprDup(pParse->db, pAppend->a[i].pExpr, 0);
+      assert( pDup==0 || !ExprHasProperty(pDup, EP_MemToken) );
       if( bIntToNull && pDup && pDup->op==TK_INTEGER ){
         pDup->op = TK_NULL;
         pDup->flags &= ~(EP_IntValue|EP_IsTrue|EP_IsFalse);
+        pDup->u.zToken = 0;
       }
       pList = sqlite3ExprListAppend(pParse, pList, pDup);
       if( pList ) pList->a[nInit+i].sortFlags = pAppend->a[i].sortFlags;