Fix Model Adaptivity active simulation mask generation for edge case (#270)

* add fix and changelog

* Update CHANGELOG.md

Author: Snapex2409

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## latest
 
+- Fixed model adaptivity active simulation mask generation for 0 local simulations [#270](https://github.com/precice/micro-manager/pull/270)
 - Allow `initialize()` to return data that is not used by the adaptivity [#261](https://github.com/precice/micro-manager/pull/261)
 - Fixed `MicroSimulation` initialization requiring positional parameters [#255](https://github.com/precice/micro-manager/pull/255)
 - Fixed model adaptivity convergence at resolution boundaries to prevent infinite loops for out-of-range switching requests [#252](https://github.com/precice/micro-manager/pull/252)

micro_manager/adaptivity/model_adaptivity.py

@@ -453,6 +453,7 @@ def _create_active_mask(self, active_sim_ids: list, size: int) -> np.ndarray:
             active_sims = np.ones(size)
         else:
             mask = np.zeros(size)
-            mask[active_sim_ids] = 1
+            if len(active_sim_ids) > 0:
+                mask[active_sim_ids] = 1
             active_sims = mask
         return active_sims.astype(bool)