Make getBackgroundAtlasLocation not nullable

Author: Swedz

src/client/java/aztech/modern_industrialization/machines/gui/MachineScreen.java

@@ -212,13 +212,13 @@ protected void renderBg(GuiGraphics guiGraphics, float delta, int mouseX, int mo
     private void renderConfigurableSlotBackgrounds(GuiGraphics guiGraphics) {
         for (Slot slot : this.menu.slots) {
             if (slot.isActive() && slot instanceof BackgroundRenderedSlot brs) {
+                var atlas = brs.getBackgroundAtlasLocation();
                 int px = leftPos + slot.x - 1;
                 int py = topPos + slot.y - 1;
                 if (slot.getItem().isEmpty()) {
-                    var atlas = brs.getBackgroundAtlasLocation();
-                    guiGraphics.blit(atlas == null ? SLOT_ATLAS : atlas, px, py, brs.getBackgroundU(), brs.getBackgroundV(), 18, 18);
+                    guiGraphics.blit(atlas, px, py, brs.getBackgroundU(), brs.getBackgroundV(), 18, 18);
                 } else {
-                    guiGraphics.blit(SLOT_ATLAS, px, py, 0, 0, 18, 18);
+                    guiGraphics.blit(atlas, px, py, 0, 0, 18, 18);
                 }
             }
         }

src/main/java/aztech/modern_industrialization/inventory/BackgroundRenderedSlot.java

@@ -23,19 +23,18 @@
  */
 package aztech.modern_industrialization.inventory;
 
+import aztech.modern_industrialization.MI;
 import net.minecraft.resources.ResourceLocation;
-import org.jetbrains.annotations.Nullable;
 
 /**
  * Implement this on a slot to render its background automatically.
  */
 public interface BackgroundRenderedSlot {
     /**
-     * @return the {@link ResourceLocation} of the slot atlas texture to use for the slot background. When null, uses the MI slot atlas
+     * @return the {@link ResourceLocation} of the slot atlas texture to use for the slot background.
      */
-    @Nullable
     default ResourceLocation getBackgroundAtlasLocation() {
-        return null;
+        return MI.id("textures/gui/container/slot_atlas.png");
     }
 
     default int getBackgroundU() {