Turn static void array into ubyte one

I am surprised this compiles with `dmd` but latest LDC alpha (also 2.065 frontend) reports:
```
Running ldmd2...
../../../../.dub/packages/vibe-d-0.7.21-alpha.3/source/vibe/core/core.d(1144): Error: static arrays of voids have no default initializer
```
Which makes sense. `void` does not have any size and having static array of those is totally undefined.