Fix "in" field not in project and resource form templates

src/coscine/form.py

@@ -108,7 +108,9 @@ class FormField:
 		Preset selection of values - no other value except for these values
 		can be specified. Think of it as a class defined in the profile.
 		"""
-		return self._data["in"]
+		if "in" in self._data:
+			return self._data["in"]
+		return None
 
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