When the left-most table of a RIGHT JOIN is implemented as a co-routine,

make sure all its columns are flushed to NULL when it finishes so that
they appear to be NULL during the RIGHT JOIN post-processing.

FossilOrigin-Name: f84b2beca719758979d7a5a63c3d16d5121a7518b3fbe5039af474a83dd569c2

src/select.c

@@ -6755,6 +6755,9 @@ int sqlite3Select(
       pItem->pTab->nRowLogEst = pSub->nSelectRow;
       pItem->fg.viaCoroutine = 1;
       pItem->regResult = dest.iSdst;
+      if( pItem->fg.jointype & JT_LTORJ ){
+        sqlite3VdbeAddOp3(v, OP_Null, 0, dest.iSdst, dest.iSdst+dest.nSdst-1);
+      }
       sqlite3VdbeEndCoroutine(v, pItem->regReturn);
       sqlite3VdbeJumpHere(v, addrTop-1);
       sqlite3ClearTempRegCache(pParse);