FVimFontLineHeight '0' will freeze or hang process sometimes

[nree]

I don't know why anyone would want 0 line height, but I see this issue when testing out the other issues.

Expected: Line height goes to 0, everything looks weird. Can still use / input.

What happens: Sometimes it freezes, can not input or see any render, but can close normally. Sometimes the process hangs and cannot input anything and need to terminate process (ctrl alt del).

Reproduce:

1. Need to open decent size file, I use fvim/ui.fs
2. (Optional) Have decent line height already :FVimFontLineHeight 'default'
3. Set line height 0 :FVimFontLineHeight '0' Sometimes will freeze, sometimes will hang Sometimes will work (this is only true if file isn't big enough for me)

Btw I have decent speed machine (Ryzen 3600, 16GB memory, geforce 1050)

Not big deal because I don't think anyone would set line height to 0 on purpose. But maybe bug appears for real values but the difference in line height is too big?

[nree]

Did more test:

+30.0 -> -10.0 = OK +30.0 -> -30.0 = BAD

So even real values that are huge still ok, only really big ones that no one would do are bad. But probably need to confirm with someone with lower spec computer?

[yatli]

added a few guards to line height so it should be fixed now.

[nree]

🏄‍♂️

works better than before. no crash, and can handle +50.0 -> -50.0 more smooth now, no hang.