remove_fin: fix bug in remove_fin_det_weak

* wrap/python/tests/remfin.py: New file.
* wrap/python/tests/Makefile.am: Add it.
* src/twaalgos/remfin.cc (remove_fin_det_weak): Purge dead states.

wrap/python/tests/remfin.py

@@ -0,0 +1,37 @@
+import spot
+
+# This test used to trigger an assertion (or a segfault)
+# in scc_filter_states().
+aut = spot.automaton("""
+HOA: v1
+States: 3
+Start: 1
+AP: 1 "a"
+Acceptance: 1 Inf(0)
+--BODY--
+State: 0 {0}
+[t] 0
+State: 1
+[!0] 0
+[0] 2
+State: 2
+[t] 2
+--END--
+""")
+aut.prop_inherently_weak()
+aut = spot.dtwa_complement(aut)
+aut = spot.scc_filter_states(aut)
+assert(aut.to_str('hoa') == """HOA: v1
+States: 2
+Start: 0
+AP: 1 "a"
+acc-name: co-Buchi
+Acceptance: 1 Fin(0)
+properties: trans-labels explicit-labels state-acc deterministic
+properties: inherently-weak
+--BODY--
+State: 0
+[0] 1
+State: 1
+[t] 1
+--END--""")