Fixed issue #36 (Uploading empty files)

[T-vK]

I fixed the issue by doing an initial empty write. This ensures that the file will be created even if it's empty.
I also made sure that chunks will have a length property by making it an empty array if the file is empty.

[AndiDittrich]

Thanks for your contribution!

i believe that it's not required to write any data to the file in case it is empty. open..close should create it.

./nodemcu-tool terminal
[SerialTerminal] Starting Terminal Mode - press ctrl+c to exit

> file.open("x.lua", "w+")
> file.close()
> [SerialTerminal] Connection closed

./nodemcu-tool fsinfo
[NodeMCU-Tool] Connected
[NodeMCU] Version: 2.0.0 | ChipID: 0xd1aa | FlashID: 0x1640e0
[NodeMCU] Free Disk Space: 3265 KB | Total: 3366 KB | 14 Files
[NodeMCU] Files stored into Flash (SPIFFS)
          |- f1.lua (18 Bytes)
          |- f3.lua (19 Bytes)
          |- f2.lua (19 Bytes)
          |- x.lua (0 Bytes)

[T-vK]

Well, initially I tried that, but I ended up with:

[NodeMCU-Tool] Uploading "e.lua" >> "e.lua"...                                                                                                                                                              
[NodeMCU-Connector] Transfer-Mode: hex                                                                                                                                                                      
 ░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░ 1% | ETA: undefineds | 1/100[NodeMCU-Tool] File Transfer complete!                                                                                                
 ░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░ 1% | ETA: nulls | 1/100

I assumed it failed.
But now that you mention it, I think you are probably right. I think we just have to ensure the callback is called even when the chunk is empty. I'll make some adjustments and push another commit.

[T-vK]

Seems to work pretty well. Empty files can be uploaded without additional writes and the download works without any issues, too.

nodemcu-tool upload g.lua
[NodeMCU-Tool] Project based configuration loaded
[NodeMCU-Tool] Connected
[NodeMCU] Version: 2.0.0 | ChipID: 0x1676b1 | FlashID: 0x1640e0
[NodeMCU-Tool] Uploading "g.lua" >> "g.lua"...
[NodeMCU-Connector] Transfer-Mode: hex
[NodeMCU-Tool] File Transfer complete!

nodemcu-tool download g.lua
[NodeMCU-Tool] Project based configuration loaded
[NodeMCU-Tool] Local file "g.lua" already exist - new file renamed to "g.lua.1493478143226"
[NodeMCU-Tool] Connected
[NodeMCU] Version: 2.0.0 | ChipID: 0x1676b1 | FlashID: 0x1640e0
[NodeMCU-Tool] Downloading "g.lua" ...
[NodeMCU-Connector] Transfer-Encoding: base64
[NodeMCU-Tool] Data Transfer complete!
[NodeMCU-Tool] File "g.lua.1493478143226" created

[AndiDittrich]

Great :) v2.1.1 is out inlcuding your fix - thank you!