Fix failure where launch type command is found and can't sync.

[tjsr]

When we try to sync existing commands, it will iterate through the ones returned and already recognised by this discord app, and may return command such as launch - which has a type/index of 4. This goes out of range, so crashes the parse command when it tries to set this within a map that doesn't exist.

For now the simple solution will be to just put a null check on that array index in case you get any unknown command types come back - eg, new features that have come along since this library was written, as is the case here.

But It would also be a good idea to not only have these checks, but update the library to use the latest ApplicationCommandType definitions that include these new unrecognised types.