[CINN] Fix crash in CheckTensorIsContinuous due to invalid as_var_ref() on constants

Author: baoqiwen

paddle/cinn/ir/group_schedule/config/group_tile_util.cc

@@ -184,10 +184,10 @@ bool CheckBroadcastTensorIsContinuous(
     if (!iter_var2value.count(iter_var)) {
       return false;
     }
+  
     ir::Expr iter_value = iter_var2value.at(iter_var);
 
-    if (!iter_value.as_var() && !iter_value.is_constant()) return false;
-
+    if (!iter_value.as_var()) return false;
     for (; loop_idx < for_iters.size(); ++loop_idx) {
       if (for_iters[loop_idx] == iter_value.as_var_ref()) {
         break;
@@ -212,14 +212,13 @@ bool CheckTensorIsContinuous(
   for (int i = 0; i < indices.size(); ++i) {
     ir::Expr index = indices[i];
     index = optim::ArithSimplify(index);
-    if (index.is_constant()) return false;
     if (!index.is_var()) return false;
     ir::Var iter_var = index.as_var_ref();
     if (!iter_var2value.count(iter_var)) {
       return false;
     }
     ir::Expr iter_value = iter_var2value.at(iter_var);
-    if (!iter_value.as_var() && !iter_value.is_constant()) return false;
+    if (!iter_value.as_var()) return false;
     if (for_iters[i] != iter_value.as_var_ref()) {
       return false;
     }