nested grid layout lost when loading in 1 column mode

[fredericrous]

Subject of the issue

gridstack elements don't move to the top when screen is resized from mobile 1 column to standard view

Your environment

• version of gridstack.js - v7.2.3 (can reproduce on v6 as well)
• which browser/OS chrome/mac

Steps to reproduce

• navigate to https://gridstackjs.com/demo/nested_advanced.html
• obsever the widgets are all stacked up to the top
• reduce your browser's window until the one column mode triggers
• refresh the page ⚠️
• resize the window again to go out of the mobile mode
• you can observe the widgets do not get back to the place they are supposed to be

Expected behavior

I expect the widgets to be stacked up at the top of the page when I resize a small browser window (float: true)

[adumesny]

this will be harder to fix - note that I don't support 1 column by default anymore, so you have to add this for old behavior columnOpts: { breakpoints: [{w:768, c:1}] },