randomize: added doAssert(seed!=0) to avoid invalid (non-random) behavior (#10635)

Author: timotheecour

lib/pure/random.nim

@@ -513,6 +513,7 @@ proc initRand*(seed: int64): Rand =
 
  let now = getTime()
  var r2 = initRand(now.toUnix * 1_000_000_000 + now.nanosecond)
+ doAssert seed != 0 # 0 causes `rand(int)` to always return 0 for example.
  result.a0 = ui(seed shr 16)
  result.a1 = ui(seed and 0xffff)
  discard next(result)