Guard against crashes from trace_cache.pop() (#1533)

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

Author: TimPansino

newrelic/core/context.py

@@ -75,7 +75,7 @@ def __exit__(self, exc, value, tb):
                 self.trace_cache[self.thread_id] = self.restore
             else:
                 # Remove entry from cache
-                self.trace_cache.pop(self.thread_id)
+                self.trace_cache.pop(self.thread_id, None)
 
 
 def context_wrapper(func, trace=None, request=None, trace_cache_id=None, strict=True):