Fix a couple warnings

Author: Burbulinis

src/main/java/org/skriptlang/skript/bukkit/spawners/elements/expressions/spawnerentry/ExprSpawnerEntryDropChances.java

@@ -73,7 +73,7 @@ protected Float[] get(Event event, SkriptSpawnerEntry[] source) {
 	@Override
 	public void change(Event event, Object @Nullable [] delta, ChangeMode mode) {
 		EquipmentSlot[] slots = this.slots.getArray(event);
-		Float chance = delta != null ? (Float) delta[0] : null;
+		float chance = delta != null ? (float) delta[0] : 0;
 
 		for (SkriptSpawnerEntry entry : getExpr().getArray(event)) {
 			for (EquipmentSlot slot : slots) {

src/main/java/org/skriptlang/skript/bukkit/spawners/util/events/SpawnerEntryEvent.java

@@ -2,6 +2,7 @@
 
 import org.bukkit.event.Event;
 import org.bukkit.event.HandlerList;
+import org.jetbrains.annotations.NotNull;
 import org.skriptlang.skript.bukkit.spawners.util.SkriptSpawnerEntry;
 
 public class SpawnerEntryEvent extends Event {
@@ -17,7 +18,7 @@ public SkriptSpawnerEntry getSpawnerEntry() {
 	}
 
 	@Override
-	public HandlerList getHandlers() {
+	public @NotNull HandlerList getHandlers() {
 		throw new UnsupportedOperationException();
 	}