2.9.0 breaks responsiveness when multiple items are shown.

[webpro-solutions]

Issue description: I recently updated from 2.8.8 to 2.9.0 and now our responsive sliders with multiple items showing with lazy loading (which worked in 2.8.8) are having issues. When it hits the breakpoint, it adjusts to the proper size, however, it is leaving empty spaces where images should be (lazy loaded images that haven't loaded and don't ever load). There was even some overlapping of images (the dynamic positioning was off).

Demo link/slider setting: I don't have a public demo but here are the settings being used:
const theMultiCarousel = tns({
items: 1,
responsive: {
480: {
items: 2
},
768: {
items: 3
},
991: {
items: 4
}
},
container: this.targetElement,
nav: false,
slideBy: '1',
gutter: 15,
autoplay: true,
controlsText: ['', ''],
autoplayButtonOutput: false,
mouseDrag: true,
lazyload: true
});

Tiny-slider version: 2.9.0 and 2.9.1
Browser name && version: Chrome: Version 71.0.3578.98 | Firefox: 64.0 | Safari: 12.0.2 | IE 11
OS name && version: MacOS High Sierra V 10.13.6

[torsteinringnes]

Can confirm, I have the exact same issue.

[scsskid]

confirmed, rolled back, 2.8.8 works, didnt test 2.8.9 (if released)

[fatcrobat]

Same here, rolled back to 2.8.8.

[scottleblang]

Created a pull request for this issue. Changing line 1426 in src/tiny-slider.js from:
if (itemsChanged || !carousel) { updateGallerySlidePositions(); }
to
if (itemsChanged && !carousel) { updateGallerySlidePositions(); }