Catch books with invalid JSON as page content and kick the player.

This has so far oly happened once with ProtocolLib, so for now we only catch it there.
Kicking the corresponding player should prevent spamming of this error.
See also https://pastebin.com/9XQsf5rT and https://hub.spigotmc.org/jira/projects/SPIGOT/issues/SPIGOT-7155

Author: minoneer

src/main/java/me/minoneer/bukkit/bookexploit/ProtocolLibHook.java

@@ -6,6 +6,7 @@
 import com.comphenix.protocol.events.ListenerPriority;
 import com.comphenix.protocol.events.PacketAdapter;
 import com.comphenix.protocol.events.PacketEvent;
+import com.google.gson.JsonParseException;
 import org.bukkit.entity.Player;
 import org.bukkit.inventory.ItemStack;
 import org.bukkit.plugin.Plugin;
@@ -29,15 +30,33 @@ public static void activate(
             public void onPacketReceiving(PacketEvent event) {
                 final Player player = event.getPlayer();
                 ItemStack item = event.getPacket().getItemModifier().readSafely(0);
-                ItemStack filteredItem = bookFilter.filterBook(item, player, FilterAction.CREATE);
-                if (filteredItem != null) {
+                try {
+                    ItemStack filteredItem = bookFilter.filterBook(item, player, FilterAction.CREATE);
+
+                    if (filteredItem != null) {
+                        event.setCancelled(true);
+                        event.getPlayer().updateInventory();
+                        logger.log(
+                                Level.WARNING,
+                                "Player {0} {1} tried to create a book with illegal click events!",
+                                new Object[]{player.getName(), player.getUniqueId()}
+                        );
+                        if (config.getPlayerMessage() != null) {
+                            player.sendMessage(config.getPlayerMessage());
+                        }
+                    }
+                } catch (JsonParseException exception) { // thrown if the book pages contain invalid JSON
+                    logger.log(
+                            Level.SEVERE,
+                            "Detected a book with invalid page content that could not be parsed in inventory of " +
+                                    "player " + player.getName() + " (" + player.getUniqueId() + "), removing the item."
+                            ,
+                            exception
+                    );
                     event.setCancelled(true);
                     event.getPlayer().updateInventory();
-                    logger.log(Level.WARNING, "Player {0} {1} tried to create a book with illegal click events!",
-                            new Object[]{player.getName(), player.getUniqueId()});
-                    if (config.getPlayerMessage() != null) {
-                        player.sendMessage(config.getPlayerMessage());
-                    }
+                    player.kickPlayer("Invalid book content detected, please contact an administrator.");
+                    logger.log(Level.SEVERE, item.toString());
                 }
             }
         });