0.5.2 broke some emphasis conversions

[pscanf]

Describe the bug
Emphasized markdown text followed by a : character doesn't get converted to emphasized html. Other characters such as , and ; also break the conversion.

To Reproduce

// Transforms correctly with 0.5.1
require("marked")("The following _should be emphasized_:")
'<p>The following <em>should be emphasized</em>:</p>\n'

// Transforms incorrectly with 0.5.2
require("marked")("The following _should be emphasized_:")
'<p>The following _should be emphasized_:</p>\n'

1. Marked Demo
2. CommonMark Demo

Expected behavior
Emphasized markdown text followed by a : character should get converted to emphasized html.

[UziTech]

might be related to #1351 (comment)

PRs are welcome 😃