Fixes NPE on empty tooltips (#4546)

src/main/java/appeng/client/gui/AEBaseScreen.java

@@ -191,10 +191,14 @@ public abstract class AEBaseScreen<T extends AEBaseContainer> extends ContainerS
     }
 
     protected void drawTooltip(MatrixStack matrices, int x, int y, ITextComponent message) {
-        String[] lines = message.getString().split("\n"); // FIXME FABRIC
-        List<ITextComponent> textLines = Arrays.stream(lines).map(StringTextComponent::new)
-                .collect(Collectors.toList());
-        this.drawTooltip(matrices, x, y, textLines);
+        String tooltipText = message.getString();
+
+        if (!tooltipText.isEmpty()) {
+            String[] lines = tooltipText.split("\n"); // FIXME FABRIC
+            List<ITextComponent> textLines = Arrays.stream(lines).map(StringTextComponent::new)
+                    .collect(Collectors.toList());
+            this.drawTooltip(matrices, x, y, textLines);
+        }
     }
 
     // FIXME FABRIC: move out to json (?)

src/main/java/appeng/client/gui/widgets/CustomSlotWidget.java

@@ -8,6 +8,7 @@ import net.minecraft.client.gui.AbstractGui;
 import net.minecraft.entity.player.PlayerEntity;
 import net.minecraft.item.ItemStack;
 import net.minecraft.util.text.ITextComponent;
+import net.minecraft.util.text.StringTextComponent;
 
 public abstract class CustomSlotWidget extends AbstractGui implements ITooltip {
     private final int x;
@@ -39,7 +40,7 @@ public abstract class CustomSlotWidget extends AbstractGui implements ITooltip {
 
     @Override
     public ITextComponent getMessage() {
-        return null;
+        return StringTextComponent.EMPTY;
     }
 
     @Override

src/main/java/appeng/client/gui/widgets/ITooltip.java

@@ -18,7 +18,10 @@
 
 package appeng.client.gui.widgets;
 
+import javax.annotation.Nonnull;
+
 import net.minecraft.util.text.ITextComponent;
+import net.minecraft.util.text.StringTextComponent;
 
 /**
  * AEBaseGui controlled Tooltip Interface.
@@ -26,10 +29,13 @@ import net.minecraft.util.text.ITextComponent;
 public interface ITooltip {
 
     /**
-     * returns the tooltip message.
+     * Returns the tooltip message.
+     * 
+     * Should use {@link StringTextComponent#EMPTY} for no tooltip
      *
      * @return tooltip message
      */
+    @Nonnull
     ITextComponent getMessage();
 
     /**

src/main/java/appeng/fluids/client/gui/widgets/FluidSlotWidget.java

@@ -1,5 +1,6 @@
 package appeng.fluids.client.gui.widgets;
 
+import java.awt.TextComponent;
 import java.util.Collections;
 
 import com.mojang.blaze3d.matrix.MatrixStack;
@@ -12,6 +13,7 @@ import net.minecraft.entity.player.PlayerEntity;
 import net.minecraft.fluid.Fluid;
 import net.minecraft.item.ItemStack;
 import net.minecraft.util.text.ITextComponent;
+import net.minecraft.util.text.StringTextComponent;
 import net.minecraft.util.text.TranslationTextComponent;
 import net.minecraftforge.common.util.LazyOptional;
 import net.minecraftforge.fluids.FluidAttributes;
@@ -84,7 +86,7 @@ public class FluidSlotWidget extends CustomSlotWidget {
         if (fluid != null) {
             return new TranslationTextComponent(fluid.getFluidStack().getTranslationKey());
         }
-        return null;
+        return StringTextComponent.EMPTY;
     }
 
     @Override