avoid KeyError when frappy is used with an invalid instrument

base.py

@@ -155,9 +155,9 @@ class ServiceManager:
                 if cmd.startswith('PY '):
                     cmd = env.get('PY', 'python3') + cmd[2:]
                 self.commands[ins] = cmd
+        self.info = result
         if len(self.info) == 1:
             self.single_ins = list(self.info)[0]
-        self.info = result
 
     #def get_cmdpats(self, groups):
     #    return self.cmdpats