I see you're using Xaero's mini-map mod, I quite like it too.
I've discovered that using Minecraft Forge version 25.0.44 seems to work on Realms without causing the "java.lang.NullPointerException" error. You may have to reset way points, but eh.
Here's a quick link to the downloads page again.
https://files.minecraftforge.net/maven/net/minecraftforge/forge/index_1.13.2.html
Make sure you click "Show Older Versions" tab, and scroll down (quite a bit down, lol) to 25.0.44 and use the installer.
Hope this fixes it! it's what worked with me.
You'll notice that Optifine isn't showing up under mods, but unfortunately Optifine isn't compatible with Forge (or at least according to the dude who make's it forum page https://www.minecraftforum.net/forums/mapping-and-modding-java-edition/minecraft-mods/1272953-optifine-hd-fps-boost-dynamic-lights-shaders-and )
