Malformed a tag breaks message render

Getting a

logs:
```
2021-06-09T19:10:33.519Z E URL constructor: http://example.com is not a valid URL.
calculateUrlPreview/links<@webpack-internal:///1758:385:23
calculateUrlPreview@webpack-internal:///1758:384:42
_applyFormatting@webpack-internal:///1758:195:10
componentDidMount@webpack-internal:///1758:183:12
Ji@webpack-internal:///91:212:132
Sj@webpack-internal:///91:255:229
exports.unstable_runWithPriority@webpack-internal:///96:19:467
cg@webpack-internal:///91:122:325
Jj@webpack-internal:///91:248:372
yj@webpack-internal:///91:239:378
fg/<@webpack-internal:///91:123:115
exports.unstable_runWithPriority@webpack-internal:///96:19:467
cg@webpack-internal:///91:122:325
fg@webpack-internal:///91:123:63
gg@webpack-internal:///91:122:496
Ig@webpack-internal:///91:230:156
enqueueSetState@webpack-internal:///91:132:239
F.prototype.setState@webpack-internal:///93:12:369
onLoaded@webpack-internal:///1382:963:12
```

reproducing:
`/html test"`

### Version information

- **Platform**: web

For the web app:

- **Browser**: Firefox 89.0b15 (64-bit)
- **OS**: btw i use Arch
- **URL**: develop.element.io up to date