Fix in QUploaderBase

[nachodd]

When $refs.input is not setted, __geFileInput returns this.$el.getElementsByClassName and that is an array. So, for instance when pickFiles method is called, it breaks when input.click() is fired

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• Bugfix
• Feature
• Code style update
• Refactor
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Does this PR introduce a breaking change? (check one)

• Yes
• No

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Other information:

[rstoenescu]

Thank you for taking time for a PR! Much appreciate it.
This will get into rc.1.

[nachodd]

Glad to help this awesome framework!