[Sparse] Fix indices (#47190)

* fix indices

paddle/phi/infermeta/sparse/unary.cc

@@ -20,7 +20,11 @@ namespace phi {
 namespace sparse {
 
 void IndicesInferMeta(const MetaTensor& x, MetaTensor* out) {
-  out->set_dims({-1});
+  // TODO(zhangkaihuo) Currently, we cannot get sparse_dim from tensor.
+  // correct shape is: shape[0] = x.sparse_dim()
+  // In the 3D point cloud model:
+  // the input x is 5-D tensor, non_zero_elements is 1-D tensor
+  out->set_dims({x.dims().size() - 1, -1});
   out->set_dtype(DataType::INT32);
   out->set_layout(DataLayout::NCHW);
 }