add -w improvement: wrap multiple files in one dir

  > ipfs add a b c
  added Qmbvkmk9LFsGneteXk3G7YLqtLVME566ho6ibaQZZVHaC9 a
  added QmR9pC5uCF3UExca8RSrCVL8eKv7nHMpATzbEQkAHpXmVM b
  added QmetGxZTgo8tYAKQH1KLsY13MxqeVHbxYVmvzBzJAKU6Z7 c
  added QmXg3WHLcjnz4ejeYF6FKVBkb4m1oKjQmF5fEWL9M1uQF3

  > ipfs ls QmXg3WHLcjnz4ejeYF6FKVBkb4m1oKjQmF5fEWL9M1uQF3
  Qmbvkmk9LFsGneteXk3G7YLqtLVME566ho6ibaQZZVHaC9 10 a
  QmR9pC5uCF3UExca8RSrCVL8eKv7nHMpATzbEQkAHpXmVM 10 b
  QmetGxZTgo8tYAKQH1KLsY13MxqeVHbxYVmvzBzJAKU6Z7 10 c

License: MIT
Signed-off-by: Juan Batiz-Benet <juan@benet.ai>

files/multipartfile.go

@@ -68,6 +68,10 @@ func (f *MultipartFile) NextFile() (File, error) {
 }
 
 func (f *MultipartFile) FileName() string {
+	if f == nil || f.Part == nil {
+		return ""
+	}
+
 	filename, err := url.QueryUnescape(f.Part.FileName())
 	if err != nil {
 		// if there is a unescape error, just treat the name as unescaped