Mermaid as Image not working

[NicoStrecker]

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Describe the bug
When i insert a Mermaid-Diagram with: + > Advanced > Mermaid... > as Image
and the mermaid contains <br> only a placeholder image is displayed not the actual diagram.
It would be better to clean this up or notify the user.

To Reproduce
Steps to reproduce the behavior:

1. Go to ' + > Advanced > Mermaid...`
2. Choose Image
3. Insert

flowchart TB
 alice --> Bob["Bob the<br>Builder"]

Loading

4. See error
   Expected behavior
   Display a warning or silently remove the linebreaks

Screenshots
If applicable, add screenshots to help explain your problem.

draw.io version (In the Help->About menu of the draw.io editor):

• draw.io version 26.1.0

Desktop (please complete the following information):

• OS: Windows
• Browser Edge
• Browser Version 134.0.3124.51

I tested the problem in incognito/private mode with all browser extensions switched off, write "yes" below:

• yes

Additional context
Add any other context about the problem here.