Use weak caches for custom textures

src/main/kotlin/util/collections/listutil.kt

@@ -0,0 +1,9 @@
+
+package moe.nea.firmament.util.collections
+
+fun <T, R> List<T>.lastNotNullOfOrNull(func: (T) -> R?): R? {
+    for (i in indices.reversed()) {
+        return func(this[i]) ?: continue
+    }
+    return null
+}