[Dashboard] Adding charts from new samples data in Dashboard edit mode throws unexpected error

[ktmud]

Screenshots

Adding the new sample charts from the video_game_sales dataset to a new dashboard in the Edit mode will render the chart with an unexpected error, which seems to come from trying to getting datasource:

The error message says "Cannot find viz object"

Saving the dashboard and refresh the whole page, the charts can correctly render.

How to reproduce the bug

1. Duplicate a sample dashboard (e.g. "Sales Dashboard" and "FCC New Coder Survey 2018") and check "Also duplicate chart":
   
2. Go to dashboard edit mode
3. Add the chart from the sample dataset

Environment

Latest master

Checklist

Make sure to follow these steps before submitting your issue - thank you!

• I have checked the superset logs for python stacktraces and included it here as text if there are any.
• I have reproduced the issue with at least the latest released version of superset.
• I have checked the issue tracker for the same issue and I haven't found one similar.

Additional context

Add any other context about the problem here.

[junlincc]

removing p1 tag, this is only happening to the new added sample charts.

[junlincc]

@ktmud do you know why the new samples data is not showing in the data table? is it also related?

[ktmud]

I'm not sure because I can't reproduce.

However, may I report another cosmetic issue:

Is this drop-shadow intended?

[junlincc]

Is this drop-shadow intended?

we didn't have a design for Data table section due to time constraints. we are merely using whatever comes with the component, i believe. it doesn't bother me much, but i agree the entire Explore page still needs a lot of cosmetic improvement. @Mihir14