Fix.

Signed-off-by: Daniel Scheffler <danschef@gfz-potsdam.de>

gms_preprocessing/algorithms/classification.py

@@ -425,7 +425,8 @@ class kNN_SAM_Classifier(SAM_Classifier):
             self.cmap.get_subset(zslice=slice(None, 1)), label_unclassified, threshold, self.angles_deg[:, :, 0]
         )
         cmap = self.cmap
-        cmap[cmap_labelled0 == label_unclassified] = label_unclassified
+        if label_unclassified in cmap_labelled0:
+            cmap[cmap_labelled0 == label_unclassified] = label_unclassified
 
         return cmap