xpdrops: fix recoloring xpdrops with hide skill icons on

The widget child array is filled with nulls to hide the sprites. It is also
valid for the child array to have null entries in it in general, but that does
not happen otherwise.

runelite-client/src/main/java/net/runelite/client/plugins/experiencedrop/XpDropPlugin.java

@@ -28,6 +28,7 @@ import com.google.inject.Provides;
 import java.util.Arrays;
 import java.util.EnumMap;
 import java.util.Map;
+import java.util.Objects;
 import java.util.stream.IntStream;
 import javax.inject.Inject;
 import net.runelite.api.Client;
@@ -112,6 +113,7 @@ public class XpDropPlugin extends Plugin
 		final IntStream spriteIDs =
 			Arrays.stream(children)
 				.skip(1) // skip text
+				.filter(Objects::nonNull)
 				.mapToInt(Widget::getSpriteId);
 
 		int color = 0;