add comment clarifying null supression

update as many singleblock machines to mui2

Author: ghzdude

src/main/java/gregtech/api/recipes/RecipeMapBuilder.java

@@ -286,6 +286,7 @@ public RecipeMapBuilder(@NotNull String unlocalizedName, @NotNull B defaultRecip
         RecipeMapUI<?> ui = new RecipeMapUI<>(recipeMap, modifyItemInputs, modifyItemOutputs, modifyFluidInputs,
                 modifyFluidOutputs, isGenerator);
         if (usesMui2) {
+            // if "usesMui2" is true, then "mapUIBuilder" is not null
             // noinspection DataFlowIssue
             this.mapUIBuilder.accept(new RecipeMapUIBuilder(ui));
         } else {