Mobile navbar above black mask

[TheTrigger]

Overview of the problem

Buefy version: [0.7.1]
OS/Browser: Android 9 - OnePlus6 - Chrome 71.0.3578.99

Steps to reproduce

1. Navigate https://buefy.github.io/documentation/dropdown/ with Android Phone
2. Open full screen Dropdown (purple Click me!)

Expected behavior

The bar should not be on top

Actual behavior

The navbar is visible above on the black mask

EDIT

Same behavior with desktop, just resize the window

[MRR0GERS]

Can confirm, this is also happening in 0.7.2. Any z-index value over 9 for the navbar causes the problem.

[yxngl]

buefy/src/scss/components/_dropdown.scss

Line 9 in a06eed4

z-index: 10;

Bulma navbar has z-index of 30 and modal has 40. Probably should be larger than that.
Tooltip in Buefy uses 888.