Do not leak null characters into the #"" encoding

src/preserves.nim

@@ -1039,7 +1039,11 @@ proc concat[E](result: var string; pr: Preserve[E]) =
   of pkString:
     result.add escapeJson(pr.string)
   of pkByteString:
-    if sequtils.any(pr.bytes, proc (b: byte): bool = b.char in {'\20'..'\21', '#'..'[', ']'..'~'}):
+    if pr.bytes.allIt(char(it) in {' '..'!', '#'..'~'}):
+      result.add("#\"")
+      result.add(cast[string](pr.bytes))
+      result.add('"')
+    else:
       if pr.bytes.len > 64:
         result.add("#[") #]#
         result.add(base64.encode(pr.bytes))
@@ -1051,10 +1055,6 @@ proc concat[E](result: var string; pr: Preserve[E]) =
           result.add(alphabet[int(b shr 4)])
           result.add(alphabet[int(b and 0xf)])
         result.add('"')
-    else:
-      result.add("#\"")
-      result.add(cast[string](pr.bytes))
-      result.add('"')
   of pkSymbol:
     result.add(escapeJsonUnquoted(pr.symbol))
   of pkRecord: