Weird dependency on Smart Slider 3?

Slide Anything shows errors when saving my slider ONLY WHEN SMART SLIDER 3 IS DISABLED.

Errors:
PHP Notice: Undefined index: sa_showcase_width in C:\wamp64\…\slide-anything-admin.php on line 2405
PHP Notice: Undefined index: sa_showcase_width_tab in C:\wamp64\…\wp-content\plugins\slide-anything\php\slide-anything-admin.php on line 2411
PHP Notice: Undefined index: sa_showcase_width_mob in C:\wamp64\…\wp-content\plugins\slide-anything\php\slide-anything-admin.php on line 2417

Steps I took:
I installed Smart Slider 3 and tried it out.
I installed Slide Anything and created a test slider with 3 slides. All worked fine.
I disabled Smart Slider 3.
I opened SA, updated the text on my slide, then clicked [Update].
Saw the error messages.
Enabled Smart Slider 3.
Opened my slide in SA and clicked [Update].
Worked fine – no error messages.
I disabled Smart Slider 3.
I opened SA and clicked [Update].
Saw the error messages.
(same occurs with the sample slider)