bug(fcsfile): fix recursion when file has no spill string

Author: gegnew

cellengine/resources/fcs_file.py

@@ -36,7 +36,8 @@ class FcsFile(DataClassMixin):
     sample_name: Optional[str] = field(default=ReadOnly(optional=True))  # type: ignore
     size: int = field(default=ReadOnly())  # type: ignore
     _spill_string: Optional[str] = field(
-        metadata=config(field_name="spillString"), default=None
+        metadata=config(field_name="spillString"),
+        default=None,
     )
 
     def __repr__(self):
@@ -275,9 +276,12 @@ def spill_string(self):
         if self._spill_string:
             return self._spill_string
         else:
-            ss = ce.APIClient().get_fcs_file(self.experiment_id, self._id).spill_string
-            self._spill_string = ss
-            return ss
+            ss = ce.APIClient().get_fcs_file(self.experiment_id, self._id, as_dict=True)
+            if ss["spillString"]:
+                self._spill_string = ss["spillString"]
+            else:
+                self._spill_string = ""
+        return self._spill_string
 
     def get_events(
         self, inplace: bool = False, destination=None, **kwargs