more reasonable path_length for MergedEdge

Author: Stevengre

pyk/src/pyk/kcfg/kcfg.py

@@ -541,7 +541,7 @@ def path_length(_path: Iterable[KCFG.Successor]) -> int:
         elif type(_path[0]) is KCFG.Edge:
             return _path[0].depth + KCFG.path_length(_path[1:])
         elif type(_path[0]) is KCFG.MergedEdge:
-            return sum(edge.depth for edge in _path[0].edges) + KCFG.path_length(_path[1:])  # todo: check this
+            return min(edge.depth for edge in _path[0].edges) + KCFG.path_length(_path[1:])  # todo: check this
         raise ValueError(f'Cannot handle Successor type: {type(_path[0])}')
 
     def extend(