bug: attempt to calculate the remainder with a divisor of 0

[foxyseta]

Empty server lists in user config are not handled gracefully:

╭Search ─────────────────────────────────────────────────────────────────────────────────────────╮╭status──────────╮
│no/thread '<unnamed>' panicked at fetcher/src/utils.rs:164:36:                                  ││Fetch playlist..
  0: rust_begin_unwind─────────────────────────────────────────attempt to calculate the remainder with a divisor of
zerortcut ────────────   1: core::panicking::panic_fmt─────────────────────────────────────────────────────────────╮
│Trestack backtrace:  ││Title                            2: core::panicking::panic_const::panic_const_rem_by_zero  │
│Youtube Community    ││
3: ytui_music::communicator::communicator::{{closure}}                                                             │
│My playlist          ││                              note: Some details are omitted, run with `RUST_BACKTRACE=full`
 for a verbose backtrace.                                                                                          │
│Search               ││ fish: Job 1, 'RUST_BACKTRACE=1 ytui_music  run' terminated by signal SIGABRT (Abort)      │
│                     ││                                                                                     ⏎

I guess a startup check that would be enough to stop the user from using such an illegal config.