Add a null assertion to the Macro data class

common/src/main/kotlin/fr/username404/snowygui/gui/feature/Macro.kt

@@ -14,7 +14,7 @@ data class Macro(
     @JvmField var command: String,
     override var title: String = command
 ): ButtonImpl() {
-    override fun execAction() = with(Minecraft.getInstance().player) {
+    override fun execAction(): Unit = with(Minecraft.getInstance().player!!) {
         chat(
             "/$command".let {
                 if (it.startsWith("/say") && !hasPermissions(2)) {