Fix nodata retrieval logic to ensure compatibility with rioxarray

Author: lbferreira

odc/geo/_xr_interop.py

@@ -1025,10 +1025,10 @@ def nodata(self) -> Nodata:
 
         for k in ["nodata", "_FillValue"]:
             nodata = attrs.get(k, ())
-            if nodata == ():
+            if nodata is ():
                 nodata = encoding.get(k, ())
 
-            if nodata == ():
+            if nodata is ():
                 continue
 
             if nodata is None: