Revert "default chunk within chunkMap to 0"

This reverts commit 2177d62.

Author: luigiplr

src/index.js

@@ -219,8 +219,6 @@ class MiniCssExtractPlugin {
   getCssChunkObject(mainChunk) {
     const obj = {};
     for (const chunk of mainChunk.getAllAsyncChunks()) {
-      obj[chunk.id] = 0;
-
       for (const module of chunk.modulesIterable) {
         if (module.type === NS) {
           obj[chunk.id] = 1;