only guard add_item

Author: sl0thentr0py

sentry-ruby/lib/sentry/telemetry_event_buffer.rb

@@ -37,8 +37,6 @@ def initialize(configuration, client, event_class:, max_items:, max_items_before
     end
 
     def flush
-      return self if @mutex.owned?
-
       @mutex.synchronize do
         return if empty?
 

sentry-ruby/spec/support/shared_examples_for_telemetry_event_buffers.rb

@@ -154,6 +154,7 @@
       3.times { subject.add_item(event) }
 
       expect(items_sent).not_to be_empty
+      expect(string_io.string).not_to include("deadlock")
     end
   end