ls370res: do not raise in read_rdgrng error when channel is disabled

Change-Id: I565e5cd74cf7f12bfd5eea9e8867117154461017

frappy_psi/ls370res.py

@@ -278,7 +278,12 @@ class ResChannel(LakeShoreIO, Channel):
         vexc = 0 if excoff or iscur else exc
         if (rng, iexc, vexc) != (self.range, self.iexc, self.vexc):
             self._last_range_change = time.monotonic()
-        self.range, self.iexc, self.vexc = rng, iexc, vexc
+        try:
+            self.range, self.iexc, self.vexc = rng, iexc, vexc
+        except Exception:
+            # avoid raising errors on disabled channel
+            if self.enabled:
+                raise
 
     @CommonWriteHandler(rdgrng_params)
     def write_rdgrng(self, change):