An issue with "Image Widget" custom sizes

[ramiy]

Description

When you set custom image sizes on "Image Widget", and you enter only the width or the only the height, you get a PHP notice.

PHP Notices

Missing width notice:

[06-May-2017 13:48:48 UTC] PHP Notice: Undefined offset: 0 in C:\xampp\htdocs\elementor\wp-content\plugins\elementor\includes\libraries\bfi-thumb\bfi-thumb.php on line 792

[06-May-2017 13:48:48 UTC] PHP Notice: Undefined offset: 0 in C:\xampp\htdocs\elementor\wp-content\plugins\elementor\includes\libraries\bfi-thumb\bfi-thumb.php on line 797

Missing height notice:

[06-May-2017 13:51:41 UTC] PHP Notice: Undefined offset: 1 in C:\xampp\htdocs\elementor\wp-content\plugins\elementor\includes\libraries\bfi-thumb\bfi-thumb.php on line 793

[06-May-2017 13:51:41 UTC] PHP Notice: Undefined offset: 1 in C:\xampp\htdocs\elementor\wp-content\plugins\elementor\includes\libraries\bfi-thumb\bfi-thumb.php on line 797

Steps to reproduce

1. turn on your debug log.
2. Drag a new "Image Widget" to any section.
3. Select a "Custom" image size.
4. Set only the image "Width", no "Height".
5. Save the page and view the page on your front-end.
6. Now check out the log.

Environment

• WordPress 4.7.4
• Elementor 1.4.5

Screenshot

[KingYes]

Thanks!