fix: exclude air from item hover events (Item must be non-empty)

Author: Euphillya

Insights-API/src/main/java/dev/frankheijden/insights/api/config/Messages.java

@@ -86,7 +86,7 @@ private <T> Component addHover(Component component, T element, Component display
 
             if (obj instanceof Material material) {
                 var key = material.getKey();
-                if (material.isItem()) {
+                if (material.isItem() && !material.isAir()) {
                     return component.hoverEvent(HoverEvent.showItem(
                             net.kyori.adventure.key.Key.key(key.getNamespace(), key.getKey()),
                             1