Check for None result in gRPC (open-telemetry#3380)

Author: kevmodo

instrumentation/opentelemetry-instrumentation-grpc/src/opentelemetry/instrumentation/grpc/_client.py

@@ -165,7 +165,7 @@ def _intercept(self, request, metadata, client_info, invoker):
                 span.record_exception(exc)
                 raise exc
             finally:
-                if not result:
+                if result is None:
                     span.end()
         return self._trace_result(span, rpc_info, result)