Fix wrong assert if padding is disabled

[simc]

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[inikulin]

@leisim Could you give more context for the issue that this one fixes, please? Regression test would be useful too

[simc]

@inikulin This assert assert!(output.len() >= input.len() + block_size); requires the output size to be greater than the input size to make sure there is enough space for padding. If no padding is used (not necessary if the input size is a multiple of the cipher block size) the output of the encryption has the exact same size as the input.

I'll add a regression test :+1:

[inikulin]

@leisim seems like needs a rebase and a regression test

[nox]

@simc Ping?