Is that actually a null result though? That sounds like a standard positive result: "We managed to show that minimum wage has no effect on employment rate".
A null result would have been: "We tried to apply Famous Theory to showing that minimum wage has no effect on employment rate but we failed because this and that".
A null result would have been: "We tried to apply Famous Theory to showing that minimum wage has no effect on employment rate but we failed because this and that".