chore: Apply suggestion from code review

Author: spotandjake

src/js/binaryen.js-post.js

@@ -2776,12 +2776,11 @@ function wrapModule(module, self = {}) {
    * Gets the memory segment with the given name.
    * 
    * @param {string} name - The name of the memory segment to get.
-   * @returns {number} A MemorySegmentRef referring to the memory segment with the given name, or `null` if no such segment exists.
+   * @returns {number} A MemorySegmentRef referring to the memory segment with the given name, or `0` if no such segment exists.
    */
   self['getMemorySegment'] = function(name) {
     return preserveStack(() => {
-      const segment = Module['_BinaryenGetMemorySegment'](module, strToStack(name));
-      return segment === 0 ? null : segment;
+      return Module['_BinaryenGetMemorySegment'](module, strToStack(name));
     });
   };
   /**

test/binaryen.js/kitchen-sink.js

@@ -1142,8 +1142,8 @@ function test_for_each() {
       data: expected_data[2].split('').map(function(x) { return x.charCodeAt(0) })
     }
   ], false);
-  assert(module.getMemorySegment(expected_names[0]) !== null);
-  assert(module.getMemorySegment("NonExistantSegment") === null);
+  assert(module.getMemorySegment(expected_names[0]) !== 0);
+  assert(module.getMemorySegment("NonExistantSegment") === 0);
   for (i = 0; i < module.getNumMemorySegments(); i++) {
     var segment = module.getMemorySegmentByIndex(i);
     var info = module.getMemorySegmentInfo(segment);