[fix]: error when upload in cancelled and limit max percentage

[zluipaiva]

Related Issue (if any)

Closes: #33

Describe the add-ons or changes you've made

Modified the upload functions to not execute when files.length is 0.
Also a small fix on the percentage loader to always be smaller than 100% (it used to break for very small files, e.g. an empty folder)

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Code style update (formatting, local variables)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

The same steps mentioned on #33

1. Click on "Upload" button
2. Select a file and confirm upload
3. Click on "Upload" again
4. Cancel the file upload

Checklist:

• My code follows the "contribution guidelines" of this project.
• I have performed a self-review of my own code.
• I have commented my code, particularly wherever it was hard to understand.
• My changes generate no new warnings.
• Any dependent changes have been merged and published in downstream modules.

[akhileshthite]

Cool.
You'll see your changes in few days once it's updated on the chrome.