Ensure that temporary SrcItem objects created by trigger processing have

either SrcItem.zName or SrcItem.pSelect defined.  Every SrcItem should have
one or the other.

FossilOrigin-Name: cef4d9e3ba586735598f03eb5e8f29072c9e6f62b0d34ddd2fb3ed1795f6e21c

src/resolve.c

@@ -1889,6 +1889,7 @@ static int resolveSelectStep(Walker *pWalker, Select *p){
     if( pOuterNC ) pOuterNC->nNestedSelect++;
     for(i=0; i<p->pSrc->nSrc; i++){
       SrcItem *pItem = &p->pSrc->a[i];
+      assert( pItem->zName!=0 || pItem->pSelect!=0 );
       if( pItem->pSelect && (pItem->pSelect->selFlags & SF_Resolved)==0 ){
         int nRef = pOuterNC ? pOuterNC->nRef : 0;
         const char *zSavedContext = pParse->zAuthContext;

src/trigger.c

@@ -987,6 +987,7 @@ static void codeReturningTrigger(
   sSelect.pSrc = &sFrom;
   sFrom.nSrc = 1;
   sFrom.a[0].pTab = pTab;
+  sFrom.a[0].zName = pTab->zName;
   sFrom.a[0].iCursor = -1;
   sqlite3SelectPrep(pParse, &sSelect, 0);
   if( pParse->nErr==0 ){