Initialize variable for all codepaths in dynamo benchmarks (#116260)

Summary:
Sometimes, the first statement that sets this variable in the try block fails due to out of memory issues and the finally block tries to delete this variable, but it was not written to in the first place.

X-link: pytorch/pytorch#116260
Approved by: https://github.com/lezcano

Reviewed By: izaitsevfb, jeanschmidt

Differential Revision: D52424766

fbshipit-source-id: 8a9b1b7c8d99148258759bef8c8f5224724bd14a

userbenchmark/dynamo/dynamobench/common.py

@@ -2304,6 +2304,7 @@ def record_status(accuracy_status, dynamo_start_stats):
             # Collect the fp64 reference outputs to be used later for accuracy checking.
             fp64_outputs = None
             model_fp64 = None
+            inputs_fp64 = None
             try:
                 model_fp64, inputs_fp64 = cast_to_fp64(
                     self.deepcopy_and_maybe_ddp(model),