Fix `tm_downloaded` init when tied file not set or missing

[pyroscope]

pyrocore/src/pyrocore/data/config/rtorrent.d/timestamps.rc

Lines 29 to 32 in 7691477

	method.insert = pyro._tm_downloaded_stat, simple|private,\
	"execute.capture=sh,-c,\"echo -n \$(stat -c %Y \\\"$1\\\")\",getDownloadedDate,(d.tied_to_file)"
	method.insert = pyro._tm_downloaded_init, simple|private,\
	"d.custom.set=tm_downloaded,(cat,(pyro._tm_downloaded_stat)); d.save_resume="

Add an if/branch and return system.time for untied items, or else :

method.insert = pyro._tm_downloaded_stat, simple|private,\ 
     "execute.capture=sh, -c , \
        \"echo -n \$(stat -c %Y \\\"$1\\\" 2>/dev/null) || echo -n \$(date +'%s')\", \
        getDownloadedDate, (d.tied_to_file)"