test=release/1.4, fix hsigmoid dereference nullptr (#16770)

* test=release/1.4, fix hsigmoid dereference nullptr

* test=release/1.4, refine condition

* test=release/1.4, refine comments

Author: JiabinYang

paddle/fluid/operators/hierarchical_sigmoid_op.h

@@ -234,6 +234,8 @@ class HierarchicalSigmoidGradOpKernel : public framework::OpKernel<T> {
       zero(dev_ctx, w_grad, static_cast<T>(0.0));
       bit_code->MulGradWeight(pre_out_grad, w_grad, in);
     } else {
+      PADDLE_ENFORCE(path != nullptr,
+                     "Sparse mode should not be used without custom tree!");
       framework::Vector<int64_t> real_rows = PathToRows(*path);
       auto* w_grad =
           ctx.Output<framework::SelectedRows>(framework::GradVarName("W"));

python/paddle/fluid/layers/nn.py

@@ -5589,12 +5589,21 @@ def hsigmoid(input,
         raise ValueError(
             "num_classes must not be less than 2 with default tree")
 
+    if (not is_custom) and (is_sparse):
+        print("Sparse mode should not be used without custom tree")
+        is_sparse = False
+
+    if (not is_custom) and ((path_table is not None) or
+                            (path_code is not None)):
+        raise ValueError(
+            "only num_classes should be passed without custom tree")
+
     if (is_custom) and (path_code is None):
-        raise ValueError("path_code should not be None with costum tree")
+        raise ValueError("path_code should not be None with custom tree")
     elif (is_custom) and (path_table is None):
-        raise ValueError("path_table should not be None with costum tree")
+        raise ValueError("path_table should not be None with custom tree")
     elif (is_custom) and (num_classes is None):
-        raise ValueError("num_classes should not be None with costum tree")
+        raise ValueError("num_classes should not be None with custom tree")
     else:
         pass