Not possible to drill-through on combined cards with different amount of series

[flamber]

Describe the bug
When combining multi-series on dashboard, then it's only possible to drill-through on the same amount of series that is in the original card as the combined card has. So if original card contains 2 series, and combining with added card with 3 series, then it's not possible to drill-through on the added card's 3rd (last) series.

To Reproduce

1. Simple question > Sample Dataset > Orders > Summarize Count grouped by CreatedAt:Year - save as Q1
   
2. Simple question > Sample Dataset > Orders > Summarize "Average of Discount" and "Average of Quantity" grouped by CreatedAt:Year - save as Q2
   
3. Add Q1 to dashboard, how the card and click "Add series" and select Q2, and save dashboard:
   
4. It's possible to click Q1's line points (blue), and Q2's first series "Average of Discount" (green), but it's not possible to click Q2's "Average of Quantity" (orange) and browser console errors with following:

Firefox: Uncaught TypeError: m is null
Chrome: Uncaught TypeError: Cannot read property '0' of null
    at t.default (app-main.bundle.js?f740cf3b1da47a41d2da:5)
    at app-main.bundle.js?f740cf3b1da47a41d2da:5
    at Array.map (<anonymous>)
    at e.value (app-main.bundle.js?f740cf3b1da47a41d2da:5)
    at t.value (app-main.bundle.js?f740cf3b1da47a41d2da:5)
    at n.handleVisualizationClick (app-main.bundle.js?f740cf3b1da47a41d2da:5)
    at SVGCircleElement.t (app-main.bundle.js?f740cf3b1da47a41d2da:5)
    at SVGCircleElement.__onclick (vendor.bundle.js?f740cf3b1da47a41d2da:1)
    at x (app-main.bundle.js?f740cf3b1da47a41d2da:5)
    at SVGPathElement.<anonymous> (app-main.bundle.js?f740cf3b1da47a41d2da:5)

Information about your Metabase Installation:
Metabase 0.35.0, 0.35.4, 0.36.7, 0.37.0-rc2 - this used to work on 0.34.3