RichText: empty anchor is removed (also in classic editor)

[greatislander]

Describe the bug
When editing a paragraph containing an anchor (e.g. ) in Firefox (64.0.2, macOS 10.14.2), pressing the delete key to delete any text in the paragraph removes the anchor, regardless of the position of the cursor in relation to the anchor within the paragraph. This affects both classic blocks and paragraph blocks.

To Reproduce
Steps to reproduce the behavior:

1. In HTML mode, add an anchor to a paragraph in a classic block or paragraph block.
2. Switch to visual mode.
3. Position the cursor anywhere within the paragraph, and press the delete key to delete text.
4. Observe that the anchor disappears.

Expected behavior
The anchor should be unaffected unless the cursor directly follows the anchor icon when the delete key is pressed.

Screenshots
https://cl.ly/24307cf3c26c

Desktop (please complete the following information):

• OS: macOS 10.14.2
• Browser: Firefox
• Version: 64.0.2

Additional context

• This issue affects WordPress 5.0.3.
• The "Undo" button in the toolbar of the classic block can be used to restore the anchor. However, Gutenberg's "Undo" button does not restore an anchor deleted from a paragraph block.
• This issue also affects the Classic Editor (see: https://core.trac.wordpress.org/ticket/45992).

[ellatrix]

This works for me if the anchor has content. What's a good use case of adding on empty anchor?

[noisysocks]

Confirmed that this happens in latest development version of Gutenberg, so removing Needs Testing.

I'm not 100% sure that it's a bug, though, as it's generally not expected that one can insert arbitrary HTML (including an empty <a> tag) into any block. The only use-case for an empty anchor that I can think of is inserting a page jump e.g. <a name="you-can-link-to-here"></a>. Using an HTML block is workaround for this.