Set default value for min_periods in trade command

[BAKFR]

Using paper mode, the min_periods option was used without being defined. It would lead to date calculation returning NaN, and thus provoking errors (at least on Binance exchange).

This commit fixes this.

[DeviaVir]

👍

[olexiyb]

This change actually impacting for example sar strategy and when we run paper trading it's failing with

C:\Users\olexi\WebstormProjects\zenbot-web\packages\zenbot-api\zenbot\extensions\strategies\sar\strategy.js:32
s.sar = Math.max(s.lookback[1].high, s.lookback[0].high)
^

TypeError: Cannot read property 'high' of undefined
at Object.calculate (C:\Users\olexi\WebstormProjects\zenbot-web\packages\zenbot-api\zenbot\extensions\strategies\sar\strategy.js:32:42)

Which strategy actually was failing?

[BAKFR]

@olexiyb I don't remember, but I've tested several strategies that was failing.

Basically, before this commit, min_periods was used several times (in trades.js) without it being initialized. This was causing an error to all strategies not requiring min_periods has a strategy option.

Can you try to call the sar strategy with the min_periods defined manually ? It's just a guess, but I thing it could be explained by the default value not being set at 52 (as requested in the sar strategy), thus creating only one period in s.lookback.

Edit: Feel free to mentions me in another issue instead of commenting in this one.