Add extra null check

Author: NotRyken

common/src/main/java/dev/terminalmc/moremousetweaks/MoreMouseTweaks.java

@@ -49,7 +49,9 @@ public static void afterConfigSaved(Config config) {
     }
 
     public static void setInteractionManagerTickRate(Config.Options options) {
-        if (Minecraft.getInstance().getSingleplayerServer() == null) {
+        @Nullable Minecraft mc = Minecraft.getInstance();
+        //noinspection ConstantValue
+        if (mc != null && mc.getSingleplayerServer() == null) {
             InteractionManager.setTickRate(options.interactionIntervalMp);
         } else {
             InteractionManager.setTickRate(options.interactionIntervalSp);