replace view with reshape, check for nans

Summary: Replace view with reshape, add check for nans before mesh sampling

Reviewed By: nikhilaravi

Differential Revision: D20548456

fbshipit-source-id: c4e1b88e033ecb8f0f3a8f3a33a04ce13a5b5043

pytorch3d/structures/utils.py

@@ -191,7 +191,7 @@ def padded_to_packed(
             "Only one of split_size or pad_value should be provided."
         )
 
-    x_packed = x.view(-1, D)  # flatten padded
+    x_packed = x.reshape(-1, D)  # flatten padded
 
     if pad_value is None and split_size is None:
         return x_packed