Fix unbound local crash on handling aws lambda exception (getsentry#977)

Author: Adam Sussman

sentry_sdk/integrations/aws_lambda.py

@@ -101,6 +101,7 @@ def sentry_handler(aws_event, aws_context, *args, **kwargs):
         configured_time = aws_context.get_remaining_time_in_millis()
 
         with hub.push_scope() as scope:
+            timeout_thread = None
             with capture_internal_exceptions():
                 scope.clear_breadcrumbs()
                 scope.add_event_processor(
@@ -115,7 +116,6 @@ def sentry_handler(aws_event, aws_context, *args, **kwargs):
                     scope.set_tag("batch_request", True)
                     scope.set_tag("batch_size", batch_size)
 
-                timeout_thread = None
                 # Starting the Timeout thread only if the configured time is greater than Timeout warning
                 # buffer and timeout_warning parameter is set True.
                 if (