Panic in the edge_triangle.go.

[gdey]

When cutting out an internal "ab … bc" ring, we get a panic.

2018/08/02 17:38:20 edge_triangle.go:345: oog rng: [[985 1485] [986 1484] [986 1483] [989 1483] [991 1482] [993 1483] [993 1485] [992 1487] [989 1489] [988 1490] [987 1489] [986 1487] [988 1485] [986 1487]]
2018/08/02 17:38:20 edge_triangle.go:346: org rng: [[985 1485] [986 1483] [989 1483] [991 1482] [993 1483] [993 1485] [992 1487] [989 1489] [988 1490] [987 1489]]
2018/08/02 17:38:20 edge_triangle.go:347: bubble type ab…bc: (    2)(    3) … (    2)(    3)
2018/08/02 17:38:20 edge_triangle.go:348: bubble type ab…bc: ([989 1483])([991 1482]) … ([989 1483])([991 1482])
2018/08/02 17:38:20 edge_triangle.go:349: cur rng: [[989 1483]]
2018/08/02 17:38:20 edge_triangle.go:350: sliver : [[991 1482] [993 1483] [993 1485] [992 1487] [989 1489] [988 1490] [987 1489] [985 1485] [986 1483]]
2018/08/02 17:38:20 edge_triangle.go:345: oog rng: [[985 1485] [986 1484] [986 1483] [989 1483] [991 1482] [993 1483] [993 1485] [992 1487] [989 1489] [988 1490] [987 1489] [986 1487] [988 1485] [986 1487]]
2018/08/02 17:38:20 edge_triangle.go:346: org rng: [[985 1485] [986 1484] [986 1483] [989 1483] [991 1482] [993 1483] [993 1485] [992 1487] [989 1489] [988 1490] [987 1489] [986 1487] [988 1485] [986 1487]]
2018/08/02 17:38:20 edge_triangle.go:347: bubble type ab…bc: (   10)(    3) … (   13)(    0)
2018/08/02 17:38:20 edge_triangle.go:348: bubble type ab…bc: ([987 1489])([989 1483]) … ([986 1483])([985 1485])
2018/08/02 17:38:20 edge_triangle.go:349: cur rng: [[989 1483]]
2018/08/02 17:38:20 edge_triangle.go:350: sliver : [[986 1487] [988 1485]]
2018/08/02 17:38:20 server.go:2923: http: panic serving [::1]:60302: index out of bounds[0 - 1], start 3 end 4