Guard Buffer.prototype.latin1Slice as well

Not sure if Deno/Bun implement Buffer, but latin1Slice borders on an
implementation detail since it isn't mentioned in the docs, so we should
make sure it exists before using it.

lib/utils.js

@@ -462,7 +462,7 @@ if (typeof Buffer === 'function') {
 }
 
 let bufferToBinaryString;
-if (typeof Buffer === 'function') {
+if (typeof Buffer === 'function' && typeof Buffer.prototype.latin1Slice === 'function') {
   bufferToBinaryString = function(buf) {
     return Buffer.prototype.latin1Slice.call(buf);
   };