Fix syntax error

stechuhr_server/server.py

@@ -305,7 +305,7 @@ def filter_current_visitors(visitors: list, hours: int=24) -> list:
 
             last_movement = None
 
-            if len(incomings) == 0
+            if len(incomings) == 0:
                 # Visitor was only moving out in the last 24h, so they are not here
                 continue
             elif not len(outgoings) == 0: