Fix bstats error with unsupported permission plugins (#6190)

Fixes #5225

Author: JRoy

Essentials/src/main/java/com/earth2me/essentials/perm/impl/SuperpermsHandler.java

@@ -170,6 +170,11 @@ public String getEnabledPermsPlugin() {
                 break;
             }
         }
+
+        if (enabledPermsPlugin == null) {
+            enabledPermsPlugin = "Other";
+        }
+
         return enabledPermsPlugin;
     }
 }