Fix issue with input path being overwritten

[mgreter]

This is a partial fix for #88
Releated libsass PR: sass/libsass#794

[am11]

@mgreter, (since I don't have definite proof with steps of reproduction, so I don't want it to create an issue for it): Sometimes, I get a debug info printed on the screen where we are setting sass_option_set_option_path, sometimes it happens on setting the next option. So do we need to guard it with condition: if(output) like here? Don't we have these conditional guards on libsass side, as we pass nullptr for every empty option string we receive to libsass?

PS: Sometimes == extremely occasional (probably when I am doing some random testing and debugging some weird scenarios, I am unable to draw definite pattern for it till now)

[mgreter]

This is probably taken over from previous code!
It should be protected in libsass itself, but the code line above actually has some different meaning, since it would overwrite the previous output path in that case. You also did not include which debug info gets printed!?

[am11]

Oh I will capture it next time. It was invalid instruction or SIGILL (and the first line mentioned glibc). I will try to capture it next time.

Thanks for the clarification on settings! 👍