add a clause to support files that were stored without any data

src/index.js

@@ -156,19 +156,24 @@ Blobs.prototype.createReadStream = function (opts) {
           return server.get(key)
         })
         .then(function (result) {
-          if (!result) throw new Error('key not found: ' + key)
-
+          if (!result) {
+            throw new Error('key not found: ' + key)
+          }
           buf = result
           var nextPart = buf.pop()
-
+          if (isUndefined(nextPart)) {
+            return next(null, new Buffer(0))
+          }
           next(null, toBuffer(nextPart))
         })
         .catch(function (err) {
           next(err)
         })
     }
 
-    if (buf.length === 0) return next(null, null)
+    if (buf.length === 0) {
+      return next(null, null)
+    }
 
     next(null, toBuffer(buf.pop()))
   })

test/specific.spec.js

@@ -89,5 +89,25 @@ describe('idb-plus-blob-store', () => {
       ws.write('hello')
       ws.end()
     })
+    it('read an empty blob', (done) => {
+      const name = 'hello.txt'
+      const ws = store.createWriteStream({name}, (err, blob) => {
+        expect(err).to.not.exist
+        expect(blob.key).to.be.eql(name)
+
+        const rs = store.createReadStream({name})
+
+        rs.pipe(bl((err, res) => {
+          expect(err).to.not.exist
+          expect(res.length).to.equal(0)
+          expect(res).to.be.eql(new Buffer(0))
+
+          done()
+        }))
+      })
+
+      ws.write(new Buffer(0))
+      ws.end()
+    })
   })
 })