Add the TK_IF_NULL_ROW opcode to deal with non-NULL result columns in the
result set of a view or subquery on the RHS of a LEFT JOIN that gets flattened.

FossilOrigin-Name: 3a5860d86fadcf924316707918bf283d26c53b1473e5e67f5cff59d18c2a7742
diff --git a/src/treeview.c b/src/treeview.c
index e4f3d78..fc18825 100644
--- a/src/treeview.c
+++ b/src/treeview.c
@@ -470,6 +470,11 @@
       sqlite3TreeViewSelect(pView, pExpr->pLeft->x.pSelect, 0);
       break;
     }
+    case TK_IF_NULL_ROW: {
+      sqlite3TreeViewLine(pView, "IF-NULL-ROW %d", pExpr->iTable);
+      sqlite3TreeViewExpr(pView, pExpr->pLeft, 0);
+      break;
+    }
     default: {
       sqlite3TreeViewLine(pView, "op=%d", pExpr->op);
       break;