Safari node replacement bug

See https://bugs.webkit.org/show_bug.cgi?id=309730 for more details.

Test cases:

• Test 1 - replacing an element and removing it's next sibling as part of that replacement FAILS in Safari only
• Test 2 - same test but with a white space so there's still a sibling PASSES in all three browsers
• Test 3 - same test but replacing with a single element grouping the others PASSES in all three browsers