Don't try to verify the schema of transient table (such as generated inside
a WITH clause) when generating code for "IN table" operators.

FossilOrigin-Name: 860aa936634a60d68e3954fc408a96a9260394e0
diff --git a/src/expr.c b/src/expr.c
index 4da9d62..fca03a8 100644
--- a/src/expr.c
+++ b/src/expr.c
@@ -1581,9 +1581,11 @@
     iCol = (i16)pExpr->iColumn;
    
     /* Code an OP_VerifyCookie and OP_TableLock for <table>. */
-    iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
-    sqlite3CodeVerifySchema(pParse, iDb);
-    sqlite3TableLock(pParse, iDb, pTab->tnum, 0, pTab->zName);
+    if( pTab->pSchema ){
+      iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
+      sqlite3CodeVerifySchema(pParse, iDb);
+      sqlite3TableLock(pParse, iDb, pTab->tnum, 0, pTab->zName);
+    }
 
     /* This function is only called from two places. In both cases the vdbe
     ** has already been allocated. So assume sqlite3GetVdbe() is always