fix: npe when placing getting from cached block positions

src/main/java/net/mcbrawls/blueprint/mixin/CachedBlockPositionMixin.java

@@ -0,0 +1,17 @@
+package net.mcbrawls.blueprint.mixin;
+
+import com.llamalad7.mixinextras.injector.ModifyReturnValue;
+import net.minecraft.block.BlockState;
+import net.minecraft.block.Blocks;
+import net.minecraft.block.pattern.CachedBlockPosition;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+
+@Mixin(CachedBlockPosition.class)
+public class CachedBlockPositionMixin {
+    // fix crashes when getBlockState happens to return null
+    @ModifyReturnValue(method = "getBlockState", at = @At("RETURN"))
+    private BlockState onGetBlockState(BlockState original) {
+        return original == null ? Blocks.AIR.getDefaultState() : original;
+    }
+}

src/main/resources/blueprint.mixins.json

@@ -1,11 +1,12 @@
 {
-	"required": true,
-	"package": "net.mcbrawls.blueprint.mixin",
-	"compatibilityLevel": "JAVA_17",
-	"mixins": [
+    "required": true,
+    "package": "net.mcbrawls.blueprint.mixin",
+    "compatibilityLevel": "JAVA_17",
+    "mixins": [
+        "CachedBlockPositionMixin",
         "ServerPlayerEntityMixin"
-	],
-	"injectors": {
-		"defaultRequire": 1
+    ],
+    "injectors": {
+        "defaultRequire": 1
 	}
 }