Safe handling of ignoredSourceOutputs array

[Maksym-L]

GH issue: https://github.com/ErikReider/SwayAudioIdleInhibit/issues/7

I am adding safe(ish) memory handling for the ignoredSourceOutputs array. It fixes "segfault" caused by out-of-bound index access.

(gdb) p data->ignoredSourceOutputs[1]
$4 = 0x69682ac <error: Cannot access memory at address 0x69682ac>