Avoid passing a NULL value as the second argument to memcpy().

FossilOrigin-Name: 58e5bb491bc0e28412ca188ba8fbe94adc67b5b1e9d7c112c36011400528d577
diff --git a/src/expr.c b/src/expr.c
index 0b922cd..31e9a93 100644
--- a/src/expr.c
+++ b/src/expr.c
@@ -2678,7 +2678,7 @@
         /* Loop through each expression in <exprlist>. */
         r1 = sqlite3GetTempReg(pParse);
         r2 = sqlite3GetTempReg(pParse);
-        if( isRowid ) sqlite3VdbeAddOp2(v, OP_Null, 0, r2);
+        if( isRowid ) sqlite3VdbeAddOp4(v, OP_Blob, 0, r2, 0, "", P4_STATIC);
         for(i=pList->nExpr, pItem=pList->a; i>0; i--, pItem++){
           Expr *pE2 = pItem->pExpr;
           int iValToIns;