Img2img mask can be filled with zeroes

[vmobilis]

When using -O3 optimization, a mask can be filled with zeroes.
It looks (I didn't use debugger) like buffer with 0xFFs is ignored by some compilers and filled with 0x00. In my case, Clang does it.
This completely masks img2img result.

Also, this commit omits mask creation for txt2img and reduces memory usage.

Fixes #606.

[vmobilis]

@leejet, @stduhpf, could you please help, to not make needless commits, do I need to include util.h into main.cpp if I want to use LOG_DEBUG()?

I built successfully locally, but all GitHub Windows builds seem to fail.

[stduhpf]

It would work to include utils.h in the main example, but It would probably be best to either call sd_log_cb() directly, or to just use printf() instead of the logger.

[leejet]

This is tricky and not very intuitive, or we could use a for loop to assign the value 255 to arr's elements.

[leejet]

There is a dangling pointer issue here, arr memory is released after going out of scope, but it is still referenced by mask_image_buffer. I fixed this issue in master, please try it if it can solve your problem.

[vmobilis]

@stduhpf, using sd_log_cb() directly would require copying log_printf() functionality, I'll try to use util.h.
But I haven't figured out how yet, linker of all Windows builds can not find log_printf() body, which should be compiled in libstable-diffusion.a.
Maybe I need to unmangle its name.

@leejet, will LOG_DEBUG() with notice to not remove it be more convenient? I'll try your fix, thank you very much.

[vmobilis]

@leejet, yes, your commit fixed the issue, thank you very much!