chore(Oper): add input check for advanceratio

src/classes/@Oper/advanceratio.m

@@ -30,13 +30,16 @@ function advRatio = advanceratio(self, diam, app)
     % Issues: https://gitlab.uliege.be/rotare/rotare/-/issues
     %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
+    ALLOWED_APP = {'propeller', 'helicopter', 'windturbine'};
+
+    app = validatestring(app, ALLOWED_APP, mfilename(), 'app');
+
     switch app
         case 'propeller'
             advRatio = self.speed / (self.rps * diam);
 
         case {'helicopter', 'windturbine'}
             advRatio = self.speed / (self.omega * diam / 2);
-
     end
 
 end