fix: make Map constructor initialEntires nullable

Author: pebrianz

std/assembly/index.d.ts

@@ -2394,7 +2394,7 @@ interface NewableFunction extends Function {
 interface IArguments {}
 interface RegExp {}
 
-interface Map<K,V> {
+interface Map<K, V> {
   readonly size: i32;
   has(key: K): bool;
   set(key: K, value: V): this;
@@ -2406,10 +2406,10 @@ interface Map<K,V> {
   toString(): string;
 }
 
-type MapInitialEntries<K,V> = {key: K, value:V}[]
+type MapInitialEntries<K, V> = {key: K, value: V}[]
 
 interface MapConstructor {
-  new <K, V>(entries?: MapInitialEntries<K,V>): Map<K,V>;
+  new <K, V>(entries?: MapInitialEntries<K, V> | null): Map<K, V>;
 }
 
 declare const Map: MapConstructor;

std/assembly/map.ts

@@ -73,14 +73,12 @@ export class Map<K,V> {
   private entriesOffset: i32 = 0;
   private entriesCount: i32 = 0;
 
-  constructor(initialEntries: MapInitialEntries<K,V> = []) {
-    let entriesLength = initialEntries.length;
-
-    if (entriesLength > 0) { 
-      if (entriesLength >= this.entriesCapacity) this.bucketsMask = entriesLength;
+  constructor(initialEntries: MapInitialEntries<K,V> | null = null) {
+    if (initialEntries) { 
+      if (initialEntries.length >= this.entriesCapacity) this.bucketsMask = initialEntries.length;
       this.rehash((this.bucketsMask << 1) | 1);
 
-      for (let i = 0; i < entriesLength; i++) {
+      for (let i = 0; i < initialEntries.length; i++) {
         let key = initialEntries[i].key;
         let value = initialEntries[i].value;
         let hashCode = HASH<K>(key);