fix SDPA fx pass (#85)

ai_edge_torch/generative/fx_passes/remove_sdpa_zero_mask_pass.py

@@ -40,7 +40,7 @@ def call(self, exported_program: torch.export.ExportedProgram):
         if self.is_zero_tensor_node(source):
           # Remove the mark_tensor call on the mask input by
           # replacing the target with an identity function.
-          node.target = lambda *args, **kwargs: args[0]
+          node.target = lambda *args, **kwargs: torch.zeros_like(args[0])
 
     exported_program.graph_module.graph.lint()
     exported_program.graph_module.recompile()