Variable mode does not work with single row

### Describe the bug

I am currently using `DynamicScroller` and `DynamicScrollerItem` and they work flawless when I style the `DynamicSCrollerItem` with CSS. However, if the scroller item has a css class to make the item span the entire row it breaks:

```
// xs12 uses this css class
flex-basis: 100%;
flex-grow: 0;
max-width: 100%;
```


Using 50% to get two columns or even 33% for 3 columns works fine too. For some reason variable mode does not like it when we have the item span the entire row

```
flex-basis: 50% // works with 33%
flex-grow: 0
max-width: 50% // works with 33%
```

### Reproduction

```

```

### System Info

```shell
System:
OS: macOS 13.1
CPU: (16) x64 Intel(R) Core(TM) i9-9980HK CPU @ 2.40GHz
Memory: 1.98 GB / 32.00 GB
Shell: 5.8.1 - /bin/zsh
Binaries:
Node: 14.18.0 - ~/.nvm/versions/node/v14.18.0/bin/node
Yarn: 1.22.17 - ~/.nvm/versions/node/v14.18.0/bin/yarn
npm: 6.14.15 - ~/.nvm/versions/node/v14.18.0/bin/npm
Browsers:
Brave Browser: 109.1.47.171
Firefox: 109.0
Safari: 16.2
```

### Used Package Manager

npm

### Validations

- [X] Read the [docs](https://github.com/Akryum/vue-virtual-scroller/blob/master/packages/vue-virtual-scroller/README.md).
- [X] Check that there isn't [already an issue](https://github.com/Akryum/vue-virtual-scroller/issues) that reports the same bug to avoid creating a duplicate.
- [X] Check that this is a concrete bug. For Q&A open a [GitHub Discussion](https://github.com/Akryum/vue-virtual-scroller/discussions).
- [X] The provided reproduction is a [minimal reproducible example](https://stackoverflow.com/help/minimal-reproducible-example) of the bug.