Fix exception when removing self-referencing cycles

Author: avillar

ogc/bblocks/models.py

@@ -510,7 +510,7 @@ def __init__(self,
         while cycles:
             #for cycle in cycles:
             #    dep_graph.remove_edge(cycle[0], cycle[1])
-            dep_graph.remove_edges_from((cycle[0], cycle[1]) for cycle in cycles)
+            dep_graph.remove_edges_from((cycle[0], cycle[-1]) for cycle in cycles)
             cycles = list(nx.simple_cycles(dep_graph))
         self.bblocks: dict[str, BuildingBlock] = {b: self.bblocks[b]
                                                   for b in nx.topological_sort(dep_graph)