L2SS-769: Also do not allow num_pointings to be negative

tangostationcontrol/tangostationcontrol/devices/beam_device.py

@@ -161,7 +161,7 @@ class beam_device(lofar_device):
     def configure_for_initialise(self, num_pointings):
         super().configure_for_initialise()
 
-        if num_pointings > self.MAX_POINTINGS:
+        if not (0 < num_pointings <= self.MAX_POINTINGS):
             raise ValueError(f"beam_device is configured to support 0 - {self.MAX_POINTINGS} pointings, but {num_pointings} were requested")
 
         # Initialise tracking control