Add edit backpacks button to /firm storage

src/main/kotlin/util/assertions.kt

@@ -1,11 +1,18 @@
-
+@file:OptIn(ExperimentalContracts::class)
 
 package moe.nea.firmament.util
 
+import kotlin.contracts.ExperimentalContracts
+import kotlin.contracts.InvocationKind
+import kotlin.contracts.contract
+
 /**
  * Less aggressive version of `require(obj != null)`, which fails in devenv but continues at runtime.
  */
 inline fun <T : Any> assertNotNullOr(obj: T?, message: String? = null, block: () -> T): T {
+	contract {
+		callsInPlace(block, InvocationKind.AT_MOST_ONCE)
+	}
     if (message == null)
         assert(obj != null)
     else
@@ -18,6 +25,9 @@ inline fun <T : Any> assertNotNullOr(obj: T?, message: String? = null, block: ()
  * Less aggressive version of `require(condition)`, which fails in devenv but continues at runtime.
  */
 inline fun assertTrueOr(condition: Boolean, block: () -> Unit) {
+	contract {
+		callsInPlace(block, InvocationKind.AT_MOST_ONCE)
+	}
     assert(condition)
     if (!condition) block()
 }