lcErg = ""
for lnRun to alines(laLines, FileToStr(...))
    If !Empty(laLines[m.lnRun])
       lcErg = m.lcErg + laLines[m.lnRun]
    endif
next
StrToFile(...)

not optimized for large files/many lines, just a one-shot...
If you need it in production, test writing directly into file instead of
concatenating a string. Works even if there are spaces/tabs in those "Empty" lines...


HTH

thomas