NaN in priceShiftLoss if the parameter interval is not present

The beforeMap was not considered if no interval is present. So the resulting calculation would end up in an NaN. Since from/to is present, we need to initialize the beforeMap for both cases, if interval is present and if an interval is not present. This fixes this issue and adds a testcase for it.

The following call currently fails: https://midgard.thorchain.info/v2/history/depths/BTC.BTC?from=1640995261&to=1643763722. This should not return an NaN in the priceShiftLoss calculation.