Apply suggestions from code review

Co-authored-by: Tobias Nießen <tniessen@tnie.de>

src/string_bytes.cc

@@ -626,10 +626,8 @@ size_t StringBytes::hex_encode(
     size_t slen,
     char* dst,
     size_t dlen) {
-  CHECK(slen * 2 >= slen && "overflow in hex encode");
-
   // We know how much we'll write, just make sure that there's space.
-  CHECK(dlen >= slen * 2 &&
+  CHECK(dlen >= MultiplyWithOverflowCheck<size_t>(slen, 2u) &&
       "not enough space provided for hex encode");
 
   dlen = slen * 2;