Merge branch 'fix/default_concurrency' into 'master'

Fix: Consider [-1] as None

See merge request detectors/pycalibration!288

xfel_calibrate/calibrate.py

@@ -890,8 +890,8 @@ def run():
             cluster_cores = concurrency.get("cluster cores", 8)
 
             con_func = concurrency.get("use function", None)
-
-            if cvals is None:
+            # Consider [-1] as None
+            if cvals is None or cvals == [-1]:
                 defcval = concurrency.get("default concurrency", None)
                 if defcval is not None:
                     print("Concurrency parameter '{}' is taken from notebooks.py".format(cvar))