SPIGOT-7622: Fix error with Player#sendSignChange

By: md_5 <git@md-5.net>

paper-server/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java

@@ -800,6 +800,7 @@ public class CraftPlayer extends CraftHumanEntity implements Player {
 
         IChatBaseComponent[] components = CraftSign.sanitizeLines(lines);
         TileEntitySign sign = new TileEntitySign(CraftLocation.toBlockPosition(loc), Blocks.OAK_SIGN.defaultBlockState());
+        sign.setLevel(getHandle().level());
         SignText text = sign.getFrontText();
         text = text.setColor(EnumColor.byId(dyeColor.getWoolData()));
         text = text.setHasGlowingText(hasGlowingText);