Rich Text: Non-selected inline boundaries wrongly highlighted on blur

[aduth]

Related: #14120 (cc @ellatrix )

Describe the bug

Similar to what was demonstrated in #14120, it can occur that all inline boundaries of a kind appear as highlighted when deselecting a paragraph while the caret is within an inline boundary.

To reproduce

Steps to reproduce the behavior:

1. Navigate to Posts > Add New
2. Add a paragraph with bolded text
3. Add another paragraph with bolded text
4. Click within one or the other of the bolded fragments from Step 2 or Step 3
5. Click in the gutters to the left or right of the block list to deselect the current paragraph
6. Note that both bolded texts appear as highlighted

Expected behavior

Neither bolded text should appear as highlighted.

Screenshots

Desktop (please complete the following information):

• OS: macOS Mojave 10.14.4 (18E226)
• Browser: Version 74.0.3729.131 (Official Build) (64-bit)
• Gutenberg version: wordpress-develop@96649a5 (effectively WordPress 5.2-RC.2)

Additional context

It seems to be important that the highlight had at one point previously been highlighted, in order for it to appear as highlighted when deselecting the block.