When data-size attribute is on, isDropup flag got wrong value

[smiglu]

When select has a lot of option (in my case 100+) I wanted to limit it to display only the 6 options with scroll. I use attribute data-size set to 6. But when i click to open select, isDropup flag is set to true, and option show above a select but is enough space to display options below button.

probably problem is in line:
estimate = liHeight * this.selectpicker.current.elements.length + menuPadding.vert;

proposition of fix that looks like it's working:
if (this.options.size !== 'auto') {
estimate = liHeight * this.options.size + menuPadding.vert;
} else {
estimate = liHeight * this.selectpicker.current.elements.length + menuPadding.vert;
}

bootstrap-select ver. 1.13.14

[NicolasCARPi]

Would you care to make a PR?

[smiglu]

ok