Crash when opening up a redirect entry in the search screen

[DaFuqs]

Describe the bug Opening up a redirect entry in the search crashes the game.

To Reproduce Steps to reproduce the behavior:

1. Open demo book
2. Clicking on "Category Redirect Entry"
3. The game crashes

Expected behavior Either the category getting opened, or redirect entries not showing up in the search in the first place

Stacktrace

java.lang.NullPointerException: Cannot invoke "com.klikli_dev.modonomicon.client.gui.book.BookContentScreen.goToPage(int, boolean)" because "this.currentContentScreen" is null
    at com.klikli_dev.modonomicon.client.gui.BookGuiManager.openEntry(BookGuiManager.java:193)
    at com.klikli_dev.modonomicon.client.gui.BookGuiManager.openEntry(BookGuiManager.java:89)
    at com.klikli_dev.modonomicon.client.gui.book.BookSearchScreen.handleButtonEntry(BookSearchScreen.java:53)
    at net.minecraft.client.gui.components.Button.onPress(Button.java:94)
    at net.minecraft.client.gui.components.AbstractButton.onClick(AbstractButton.java:56)
    at net.minecraft.client.gui.components.AbstractWidget.mouseClicked(AbstractWidget.java:189)
    at net.minecraft.client.gui.components.events.ContainerEventHandler.mouseClicked(ContainerEventHandler.java:38)
    at com.klikli_dev.modonomicon.client.gui.book.BookPaginatedScreen.mouseClicked(BookPaginatedScreen.java:102)
    at com.klikli_dev.modonomicon.client.gui.book.BookSearchScreen.mouseClicked(BookSearchScreen.java:290)

System (please complete the following information):

• Modonomicon Version: 1.67.0; Fabric
• OS: Windows
• Minecraft Version: 1.20.1
• Modpack Link and Version, or list of mods: Just Modonomicon & Spectrum