Bug with utf-16 file

[byzod]

Reproduce steps:

1. Create a utf-16 file with any text, or use attachment: utf16demo.txt
2. Active Hex mode

Expected result: 3. Display abc, same as before

Actual result: 3. Display abcnulnulnulnulnul and crash when try to active hex mode again

platforma: windows 10 home 21H2 notepad++ version: v8.4.4 x64 hex editor version: v0.9.12