FIX: Link dialog doesn't show in Safari when caret within word

[tg-ephox]

fixes #2562

In Safari when the Range is collapsed getBoundingRect returns all zeros so use range of the startContainer in this instance

If a paragraph block is empty and the link toolbar is clicked the link dialog shows in the centre of the block which seems acceptable. Another issue exists to stop creation of a link if no text is selected.

[codecov]

Codecov Report

Merging #2584 into master will increase coverage by 2.35%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##           master    #2584      +/-   ##
==========================================
+ Coverage   31.59%   33.95%   +2.35%     
==========================================
  Files         175      177       +2     
  Lines        5307     5829     +522     
  Branches      916     1074     +158     
==========================================
+ Hits         1677     1979     +302     
- Misses       3080     3249     +169     
- Partials      550      601      +51

Impacted Files	Coverage Δ
blocks/editable/index.js	10.52% <0%> (-0.5%)	⬇️
components/higher-order/with-api-data/request.js	97.67% <0%> (-2.33%)	⬇️
blocks/url-input/index.js	1.28% <0%> (-0.42%)	⬇️
blocks/api/parser.js	97.93% <0%> (-0.18%)	⬇️
editor/sidebar/post-taxonomies/index.js	0% <0%> (ø)	⬆️
editor/modes/visual-editor/block-list.js	0% <0%> (ø)	⬆️
editor/sidebar/post-excerpt/index.js	0% <0%> (ø)	⬆️
editor/sidebar/discussion-panel/index.js	0% <0%> (ø)	⬆️
editor/sidebar/header.js	0% <0%> (ø)	⬆️
editor/sidebar/post-status/index.js	0% <0%> (ø)	⬆️
... and 11 more

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[youknowriad]

This is causing the link modal to show up under the paragraph block (instead of under the cursor position) I tested in Chrome (and the cursor was in the middle of the paragraph block)

[tg-ephox]

@youknowriad have looked at this again and I think it works quite well now. The new approach is to select a single character when the range is collapsed except if there's no text content (in the case of an empty block) where it selects the range of the container, which ends up with the link dialog centred below the empty block.

[youknowriad]

Works great thanks for the fix