Fix javadoc warnings

Spigot-API-Patches/Add-UnknownCommandEvent.patch

@@ -6,7 +6,7 @@ Subject: [PATCH] Add UnknownCommandEvent
 
 diff --git a/src/main/java/org/bukkit/event/command/UnknownCommandEvent.java b/src/main/java/org/bukkit/event/command/UnknownCommandEvent.java
 new file mode 100644
-index 00000000..73f99907
+index 00000000..19d634c3
 --- /dev/null
 +++ b/src/main/java/org/bukkit/event/command/UnknownCommandEvent.java
 @@ -0,0 +0,0 @@
@@ -70,6 +70,8 @@ index 00000000..73f99907
 +     * Sets message that will be returned
 +     * <p>
 +     * Set to null to avoid any message being sent
++     *
++     * @param message the message to be returned, or null
 +     */
 +    public void setMessage(String message) {
 +        this.message = message;