Using an if-statement in modelica

I made a simple model of a heat pump which uses sensor data to calculate its COP.

while COP = heat / power

sometimes there is no power so the system does a (cannot divide by zero). I would like these values to just be zero. So i tried an IF-statementif-statement. if power(u) = 0 then COP(y) = 0. somehow this does not work (see time 8)COP output + data. Anyone who seems to notice the problem?