Fix empty node set exception

[flo-dup]

Please check if the PR fulfills these requirements

• [x] The commit message follows our guidelines
• [x] Tests for the changes have been added (for bug fixes / features)
• [ ] Docs have been added / updated (for bug fixes / features)

Does this PR already have an issue describing the problem? No

What kind of change does this PR introduce? Bug fix

What is the current behavior? If the voltage level drawn contains a connected component with no fictitious node, a exception is thrown

What is the new behavior (if this is a feature change)? If the voltage level drawn contains a connected component with no fictitious node, a fictitious BusNode is added to the first node of the connected component set (sorted in alphabetical order)

Does this PR introduce a breaking change or deprecate an API?

• [ ] Yes
• [x] No

[sonarcloud[bot]]

Quality Gate passed

Issues
2 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud