Fixes #3086.

The exception was caused by an extremely rare type of restriction: a via-way restriction with multiple from-ways (restriction=no_entry). The following overpass query finds such restrictions:

relation[type=restriction](if:count_by_role("from") > 1);
foreach -> .r (
  way(r.r:via);
  if (count(ways) > 0) {
    .r out geom;
  }
);

Currently there are 54. But they are all invalid for various reasons like missing from/to-members, disconnected member ways etc. so we ignore them anyway. There is only one exception, namely the one that has been added only recently and caused the error. That one isn't strictly necessary, because the desired turn restrictions could be represented with a simpler mapping, but it is 'correct' tagging nonetheless. Sidenote: This specific restriction is also time-dependent, so it will typically be ignored.

Still, I somewhat see how this type of mapping can be useful and since we already had everything required in place I did not simply ignore these via-way no_entry/no_exit restrictions but added support for them.