RegExp pattern bug in preview_theme function

[wpus.org]

The theme can't be previewed if the theme path include '-' letter.
Because preview_theme function will remove the dash letter. Please refer lines 852 and 860 in theme.php file.

The current regular expression pattern:

'|[^a-z0-9_.-/]|i'

To fix it, just add one back slash before the last dash. Use the following pattern:

'|[^a-z0-9_.\-/]|i'

[ryan]

See #9329