refactor: improve socketname assignment

The code change refactors the socketname assignment in the linuxgsm.sh script. Instead of directly assigning it to "${sessionname}-$(cat "${datadir}/${selfname}.uid")", it now checks if the file "${datadir}/${selfname}.uid" exists before assigning the value. This improves error handling and prevents potential issues when the file doesn't exist.

linuxgsm.sh

@@ -36,7 +36,7 @@ tmpdir="${lgsmdir}/tmp"
 datadir="${lgsmdir}/data"
 lockdir="${lgsmdir}/lock"
 sessionname="${selfname}"
-socketname="${sessionname}-$(cat "${datadir}/${selfname}.uid")"
+[ -f "${datadir}/${selfname}.uid" ] && socketname="${sessionname}-$(cat "${datadir}/${selfname}.uid")"
 serverlist="${datadir}/serverlist.csv"
 serverlistmenu="${datadir}/serverlistmenu.csv"
 [ -n "${LGSM_CONFIG}" ] && configdir="${LGSM_CONFIG}" || configdir="${lgsmdir}/config-lgsm"