If there are no grouped sessions, do not output empty line

CHANGELOG.md

@@ -5,6 +5,7 @@
   as other tweaks
 - save and restore grouped sessions (used with multi-monitor workflow)
 - save and restore active and alternate windows in grouped sessions
+- if there are no grouped sessions, do not output empty line to "last" file
 
 ### v1.5.0, 2014-11-09
 - add support for restoring neovim sessions

scripts/save.sh

@@ -150,7 +150,9 @@ dump_grouped_sessions() {
 fetch_and_dump_grouped_sessions(){
 	local grouped_sessions_dump="$(dump_grouped_sessions)"
 	get_grouped_sessions "$grouped_sessions_dump"
-	echo "$grouped_sessions_dump"
+	if [ -n "$grouped_sessions_dump" ]; then
+		echo "$grouped_sessions_dump"
+	fi
 }
 
 # translates pane pid to process command running inside a pane