fix scripts/fetchMediaLibraryAssets.js missing some sprite assets

Assets which are referenced by a sprite but not referenced by the sound,
costume, or backdrop libraries were being missed by previous versions. I
also removed the default parameter to several methods in order to reduce
the likelihood of similar mistakes in the future.

Author: Christopher Willis-Ford

package.json

@@ -11,7 +11,7 @@
     "clean": "rimraf ./dist/ ./static/assets/",
     "compile": "rimraf ./dist/ && electron-webpack --bail --display-error-details --env.minify=false",
     "fetch": "rimraf ./static/assets/ && mkdirp ./static/assets/ && node ./scripts/fetchMediaLibraryAssets.js",
-    "dist": "npm run fetch && npm run compile -p && electron-builder",
+    "dist": "npm run build-gui && npm run fetch && npm run compile -p && electron-builder",
     "dist:dir": "npm run dist -- --dir -c.compression=store -c.mac.identity=null",
     "lint": "eslint --cache --color --ext .jsx,.js ."
   },

scripts/fetchMediaLibraryAssets.js

@@ -16,7 +16,7 @@ const describe = function (object) {
     return util.inspect(object, false, Infinity, true);
 };
 
-const collectSimple = function (library, debugLabel = 'Item', dest = new Set()) {
+const collectSimple = function (library, dest, debugLabel = 'Item') {
     library.forEach(item => {
         let md5Count = 0;
         if (item.md5) {
@@ -37,21 +37,21 @@ const collectSimple = function (library, debugLabel = 'Item', dest = new Set())
     return dest;
 };
 
-const collectAssets = function (dest = new Set()) {
-    collectSimple(libraries.backdrops, 'Backdrop', dest);
-    collectSimple(libraries.costumes, 'Costume', dest);
-    collectSimple(libraries.sounds, 'Sound', dest);
+const collectAssets = function (dest) {
+    collectSimple(libraries.backdrops, dest, 'Backdrop');
+    collectSimple(libraries.costumes, dest, 'Costume');
+    collectSimple(libraries.sounds, dest, 'Sound');
     libraries.sprites.forEach(sprite => {
         if (sprite.md5) {
             dest.add(sprite.md5);
         } else {
             console.warn(`Sprite has no MD5 property:\n${describe(sprite)}`);
         }
         if (sprite.json.costumes) {
-            collectSimple(sprite.json.costumes, `Costume for sprite ${sprite.name}`);
+            collectSimple(sprite.json.costumes, dest, `Costume for sprite ${sprite.name}`);
         }
         if (sprite.json.sounds) {
-            collectSimple(sprite.json.sounds, `Sound for sprite ${sprite.name}`);
+            collectSimple(sprite.json.sounds, dest, `Sound for sprite ${sprite.name}`);
         }
     });
     return dest;
@@ -88,7 +88,7 @@ const fetchAsset = function (md5, callback) {
 };
 
 const fetchAllAssets = function () {
-    const allAssets = collectAssets();
+    const allAssets = collectAssets(new Set());
     console.log(`Total library assets: ${allAssets.size}`);
 
     async.forEachLimit(allAssets, NUM_SIMULTANEOUS_DOWNLOADS, fetchAsset, err => {