Need to set 'min-height: 0' for blank columns.

[adsingh14]

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[royklutman]

Just to elaborate on this, it's currently set to 1px to prevent collapsing:

bootstrap/scss/mixins/_grid-framework.scss

Lines 8 to 14 in a194abb

	%grid-column {
	position: relative;
	width: 100%;
	min-height: 1px; // Prevent columns from collapsing when empty
	padding-right: ($gutter / 2);
	padding-left: ($gutter / 2);
	}

Maybe someone can explain why this is done exactly and why columns may not collapse when empty?

[MartijnCuppens]

The grid used to be float based. If a column was empty, the height would be 0 and the column to the right would move over this column because it wouldn't take any space. The min-height: 1px; was than added to fix this behaviour.

We can now safely remove this, because the new flexbox based grid doesn't have this issue.