#13 Bug in logging component + fix

[Kees]

Line 529 of file /source/StGenLog should be changed into:

if ((FS.Size = 0) and (FLogFileHeader <> '')) then begin

If you don't do this, you'll get an exception if you
use method DumpLog() when the LogFileHeader property is
an empty string.
For people who don't need a header.

Cheers, Kees