Fixes not known category in Appliances (Fixes #1156)

gns3server/controller/appliance.py

@@ -73,12 +73,16 @@ class Appliance:
         """
         Appliance data (a hash)
         """
+        try:
+            category = ID_TO_CATEGORY[self._data["category"]]
+        except KeyError:
+            category = self._data["category"]
         return {
             "appliance_id": self._id,
             "node_type": self._data["node_type"],
             "name": self._data["name"],
             "default_name_format": self._data.get("default_name_format", "{name}-{0}"),
-            "category": ID_TO_CATEGORY[self._data["category"]],
+            "category": category,
             "symbol": self._data.get("symbol", ":/symbols/computer.svg"),
             "compute_id": self.compute_id,
             "builtin": self._builtin