Don't replace empty api_key

couchpotato/core/logger.py

@@ -43,6 +43,7 @@ class CPLog(object):
             # Replace api key
             try:
                 api_key = Env.setting('api_key')
+                if api_key:
                     msg = msg.replace(api_key, 'API_KEY')
             except:
                 pass