fix: handle empty files again

Author: achingbrain

packages/ipfs-unixfs-exporter/src/resolvers/unixfs-v1/content/file.js

@@ -137,6 +137,10 @@ const fileContent = (cid, node, unixfs, path, resolve, depth, blockstore) => {
       length
     } = validateOffsetAndLength(fileSize, options.offset, options.length)
 
+    if (length === 0) {
+      return
+    }
+
     const queue = pushable({
       objectMode: true
     })

packages/ipfs-unixfs-exporter/test/exporter.spec.js

@@ -686,6 +686,14 @@ describe('exporter', () => {
     expect(data).to.deep.equal(bigFile)
   })
 
+  it('reads an empty file', async () => {
+    const data = await addAndReadTestFile({
+      file: new Uint8Array()
+    })
+
+    expect(data).to.have.property('byteLength', 0)
+  })
+
   it('returns an empty stream for dir', async () => {
     const imported = await first(importer([{
       path: 'empty'