ttq/print.py: do not print empyt matrix or gitlab user names (MR 3)

fixes #1

Signed-off-by: Robert Eckelmann <longnoserob@gmail.com>

ttq/print.py

@@ -9,9 +9,11 @@ def format_user_list(users):
     ret = []
     for user in users:
         if ttq.args.ARGS.matrix:
-            ret += [user["matrix"]]
+            if user['matrix'] != '':
+                ret += [user["matrix"]]
         else:
-            ret += [f"@{user['gitlab']}"]
+            if user['gitlab'] != '':
+                ret += [f"@{user['gitlab']}"]
 
     return ", ".join(sorted(ret))