Problem number title will be skipped due to some error when create a new one.

[Ivecia]

When we create a new problem, if there is something wrong like someone forget to add a title for the problem, the problem's id will be skipped.

For example, someone create a problem and forget to give a title, the problem should be P1007, but he find it is P1008.

See it at https://vijos.org/d/zcyz/p. (This is a school domain)