[SQL Lab] Database and Table dropdowns disconnected

[yousoph]

Expected results

In SQL Lab, the db and table dropdown options should appear attached to the dropdown

Actual results

The db and table dropdown options are showing up disconnected/detached from the dropdown

Screenshots

How to reproduce the bug

1. Go to SQL Lab
2. Click on the database dropdown
3. Select a schema
4. Click on the table dropdown

Environment

• superset version: 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.