P2: PHP Notice for breathe_color_styles()

I hope this is the right place to report a PHP Notice with p2-breathe

I am getting the following PHP Notice with Revision 57498.
> Trying to access array offset on value of type bool in inc/customizer.php line 61, 62, 64 & 65

The reason for this is this code. The `get_theme_mod()` is returning `false` by default when no settings have been saved and `isset()` is checking if the variable is null.
```php
$options = get_theme_mod( 'breathe_theme_options', null );

if ( ! isset( $options ) )
return;
```

A possible solution would be
```php
$options = get_theme_mod( 'breathe_theme_options', null );

if ( ! $options )
return;
```

Open inc/customizer.php and locate breathe_color_styles(), then reproduce the notice with no saved theme settings so get_theme_mod() returns false. Done means the PHP Notice no longer occurs in that case; no test file is named in the issue.

Written by the indexing model from the issue text.