Fix multiple open of xtbscreen.xyz in local.f90 (xtb/iff test)

[foxtran]

By some reason, at

xtb/src/local.f90

Line 278 in c3cfd38

if(set%pr_local) call open_file(iscreen,'xtbscreen.xyz','w')

xtbscreen.xyz was opened at first scope level, but the file was closed at second scope level, and therefore, if the following check was failed:

xtb/src/local.f90

Line 360 in c3cfd38

if(maxval(rklmo(5,1:n)).ge.3.)then

the close statement does not work for xtbscreen.xyz and then, at the next iteration, this file was opened at the second time.

[TyBalduf]

Do you have an example of an input where this error was occurring and that it's now resolved? Or I guess how did you find this?

The fix looks good/reasonable, I'm just curious if it's a rare case to hit or if it happens fairly regularly and has just gone unnoticed. I know some platforms/compilers are a bit more permissive about having multiple open handles to a file.

[foxtran]

I used xtb/iff test from CMake build system for finding this.

I know some platforms/compilers are a bit more permissive about having multiple open handles to a file.

I modified it.