fix crash due to empty text before a softbreak

[searKing]

Exception is thrown when a softbreak token is after strong token
This script:

var md = require('markdown-it')();
var cjk_breaks = require('markdown-it-cjk-breaks');

md.use(cjk_breaks);

md.render(`
**foo**
bar
`);

Throws an exception:

TypeError: Expected a code point, got `undefined`.

The empty text is generated by markdown-it when a strong token followed by a softbreak token.

[KSR-Yasuda]

Any update for this?
It is a considerable bug that crashes this lib.
Could you merge the fix to the latest release if no reason to hesitate, please? > repo owner, @puzrin or @rlidwka ?

[yamavol]

I'm also the one waiting to this issue to be fixed and merged.

@searKing
I think you should use continue instead of break.
This plugin still needs to remove the softbreak between CJK letters.

**山**
田

should be rendered as

<p><strong>山</strong>田</p>

but your change won't do this.