fog: fix null pointer if dimension has no fog

Minosoft would instantly crash when you go into the end, because the end has no fog but it sill tries to get the fog options.

src/main/java/de/bixilon/minosoft/gui/rendering/camera/fog/FogManager.kt

@@ -68,7 +68,8 @@ class FogManager(
         if (state.enabled != enabled) {
             state.revision++
         }
-        if (!state.enabled) return
+        state.enabled = enabled
+        if (!enabled) return
 
         val options = getOptions(effects!!)
         if (this.options == options) {