Set a default island name if unset.

plugin/src/main/java/com/alttd/cometskyblock/island/Island.java

@@ -106,7 +106,7 @@ public class Island extends YamlConfiguration {
     }
 
     public String islandName() {
-        return getString("island.islandname");
+        return getString("island.islandname", "Unnamed Island");
     }
 
     public void islandName(String islandName) {