fix missing category

Author: ImShyMike

app/controllers/api/hackatime/v1/hackatime_controller.rb

@@ -236,6 +236,9 @@ def handle_heartbeat(heartbeat_array)
 
       parsed_ua = WakatimeService.parse_user_agent(heartbeat[:user_agent])
 
+      # if category is not set, just default to coding
+      heartbeat[:category] ||= "coding"
+
       # special case: if the entity is "test.txt", this is a test heartbeat
       if heartbeat[:entity] == "test.txt"
         source_type = :test_entry