Describe the bug

When I put a b-button inside table and click on it, it will raise an error. Which is this:

TypeError: Cannot read property '$el' of undefined.
in getTbody (mixin-tbody.js?399f:32) // line 32

Steps to reproduce the bug

1.Put a b-table element
2.Make a cell (using template slot) which has a b-button in it
3.When you click on the button you will see the error.

Expected behavior

From b-button to act as a normal button

Versions

Libraries:

• BootstrapVue: 2.1.0
• Bootstrap: 4.#.#
• Vue: 2.#.#

And I know it is ok in version 2.0.4

Environment:

• Device: [PC]
• OS: [Ubuntu]
• Browser: [Chrome]
• Version: [70]