Fix scoreboard delete handler not first checking if scoreboard exists (#3324)

* Little big oversight

* Right...

Author: Ynfuien

lib/plugins/scoreboard.js

@@ -19,7 +19,8 @@ function inject (bot) {
 
       for (const position in ScoreBoard.positions) {
         const scoreboard = ScoreBoard.positions[position]
-        if (scoreboard.name === packet.name) {
+
+        if (scoreboard && scoreboard.name === packet.name) {
           delete ScoreBoard.positions[position]
           break
         }