fix filter transforms, boundary condition

Author: Kucharssim

bayesflow/adapters/transforms/concatenate.py

@@ -141,6 +141,9 @@ def log_det_jac(
         available_keys = set(log_det_jac.keys())
         common_keys = available_keys & required_keys
 
+        if len(common_keys) == 0:
+            return log_det_jac
+
         parts = [log_det_jac.pop(key) for key in common_keys]
 
         log_det_jac[self.into] = sum(parts)

bayesflow/adapters/transforms/filter_transform.py

@@ -181,4 +181,4 @@ def log_det_jac(
                 else:
                     log_det_jac[key] = ldj
 
-        return data
+        return log_det_jac