message: Replace fallback value with error in weightRandom
diff: @@ -21,6 +21,5 @@ export function weightRandom <T extends string> (specs: WeightRecord<T>): T {
  if (value <= sum) return prop
  }
  - // Should never happen, purely for type safety
  - return specsKeys[specsKeys.length - 1]
  + throw new Error('Invalid random roll.')
  }
  