Fix to block fusion

dace/transformation/interstate/block_fusion.py

@@ -1,7 +1,7 @@
 # Copyright 2019-2024 ETH Zurich and the DaCe authors. All rights reserved.
 
 from dace.sdfg import utils as sdutil
-from dace.sdfg.state import ControlFlowBlock, ControlFlowRegion, SDFGState
+from dace.sdfg.state import AbstractControlFlowRegion, ControlFlowBlock, ControlFlowRegion, SDFGState
 from dace.transformation import transformation
 
 
@@ -53,6 +53,9 @@ def can_be_applied(self, graph, expr_index, sdfg, permissive=False):
         if out_edges[0].data.assignments:
             if not in_edges:
                 return False
+            # If the first block is a control flow region, no absorbtion is possible.
+            if isinstance(self.first_block, AbstractControlFlowRegion):
+                return False
             # Fail if symbol is set before the block to fuse
             new_assignments = set(out_edges[0].data.assignments.keys())
             if any((new_assignments & set(e.data.assignments.keys())) for e in in_edges):