GetTickerPrices() and GetCandlePrices() in providers returns nothing if one pair doesn't have price data

[rbajollari]

Summary of Bug

A clear and concise description of what the 🐞 is.

Version

Please provide the output of the following commands:

• $ price-feeder version
• $ go version
• $ uname -a

Steps to Reproduce

Steps to reproduce the behavior:

1. ...

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