fix: #5064 Handle case when line has only one point

[sidharthv96]

📑 Summary

There was an edge case where the edge line only has a single point (not a "line" anymore).

• Resolves TypeError: Cannot read properties of undefined (reading 'x') #5064

📏 Design Decisions

This patch only bypasses the newly introduced bug, why a line is created with just a point needs to be investigated further.

📋 Tasks

Make sure you

• 📖 have read the contribution guidelines
• 💻 have added necessary unit/e2e tests.
• 📓 have added documentation. Make sure MERMAID_RELEASE_VERSION is used for all new features.
• 🔖 targeted develop branch

[netlify]

✅ Deploy Preview for mermaid-js ready!

Name	Link
🔨 Latest commit	7b0f6c1
🔍 Latest deploy log	https://app.netlify.com/sites/mermaid-js/deploys/6560313296472600080fb07e
😎 Deploy Preview	https://deploy-preview-5065--mermaid-js.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.

[codecov]

Codecov Report

Merging #5065 (7b0f6c1) into develop (8f733c6) will decrease coverage by 1.27%.
The diff coverage is 0.00%.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #5065      +/-   ##
===========================================
- Coverage    77.35%   76.09%   -1.27%     
===========================================
  Files          164      164              
  Lines        13869    13882      +13     
  Branches       698      700       +2     
===========================================
- Hits         10728    10563     -165     
- Misses        2987     3162     +175     
- Partials       154      157       +3     

Flag	Coverage Δ
e2e	81.18% <0.00%> (-1.59%)	⬇️
unit	42.91% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
packages/mermaid/src/utils/lineWithOffset.ts	63.82% <0.00%> (-27.35%)	⬇️

... and 9 files with indirect coverage changes