sequencenumber is not displayed with the text has a <br> tag

[goutham2688]

Describe the bug
While creating sequence diagrams with autonumber enabled, if i add a
tag to the text then the sequence number disappears from the diagram.

To Reproduce
Steps to reproduce the behavior:

1. Go to Mermaid Live Editor
2. Click on Sequence diagrams
3. Create a sequence that has both autonumber enabled and
   tag in it and is self referencing (eg., John-->John: lorem ipsum
   dolar)
4. See the sequence number is not displayed anymore in the diagram.

Expected behavior
The sequence number should be shown

Screenshots

Desktop (please complete the following information):

• Browser Firefox 73.0.1
• mermaid Version 8.4.8

[rajasekaran2003]

https://mermaid-js.github.io/mermaid-live-editor/#/edit/eyJjb2RlIjoic2VxdWVuY2VEaWFncmFtXG4gIGF1dG9udW1iZXJcblx0QWxpY2UtPj4rSm9objogSGVsbG8gSm9obiwgaG93IGFyZSB5b3U_XG5cdEFsaWNlLT4-K0pvaG46IEpvaG4sIGNhbjxici8-IHlvdSBoZWFyIG1lP1xuXHRKb2huLS0-Pi1BbGljZTogSGkgQWxpY2UsIEkgY2FuIGhlYXIgeW91IVxuXHRKb2huLS0-Pi1BbGljZTogSSBmZWVsIGdyZWF0IVxuXHRcdFx0XHRcdCIsIm1lcm1haWQiOnsidGhlbWUiOiJkZWZhdWx0In0sInVwZGF0ZUVkaXRvciI6ZmFsc2V9

still a problem on 8.5.0 with chrome