Individual linkStyle behaves differently than default linkStyle

[ppqn]

Describe the bug

When using linkStyle default, the link label is doesn't change; but when using linkstyle [number], the link label loses its background and doesn't hover over the link.

To Reproduce
Steps to reproduce the behavior:

1. Go to https://mermaidjs.github.io/mermaid-live-editor/#/edit/eyJjb2RlIjoiZ3JhcGggTFI7XG4gIEFGe0FGfVxuICBVW1VdXG4gIFUtLVdJLS0-QUY7XG4gIFUtLU5MUC0tPkFGO1xuICBsaW5rU3R5bGUgZGVmYXVsdCBmaWxsOm5vbmUsc3Ryb2tlOmdyZWVuLHN0cm9rZS13aWR0aDoxcHg7XG4gIGxpbmtTdHlsZSAxIGZpbGw6bm9uZSxzdHJva2U6cmVkLHN0cm9rZS13aWR0aDoxcHg7IiwibWVybWFpZCI6eyJ0aGVtZSI6ImRlZmF1bHQifX0

2. See the difference between WI and NLP

Code:

graph LR;
  AF{AF}
  U[U]
  U--WI-->AF;
  U--NLP-->AF;
  linkStyle default fill:none,stroke:green,stroke-width:1px;
  linkStyle 1 fill:none,stroke:red,stroke-width:1px;

Loading

Expected behavior
NLP should look like WI

Screenshots

Expected
Actual

Desktop (please complete the following information):

• OS: Windows 10
• Browser: Chrome
• Version: 8.2.3

[GDFaber]

I've stumbled across this while working on #1088 today and got it basically fixed, but need to do more testing to make sure it's working properly with different settings. So I'd like to work on this as well.

[klemmchr]

I will assign you in the meanwhile. If you verified that you fixed it, make sure to mention both issues in your pr. Thanks!

[GDFaber]

Thanks, will do.

[GDFaber]

My PR is at #1132.