allow optional lov_value property (for taipy)

[FredLL-Avaiga]

This will allow to not show a warning when an optional lov_value is not bound (think Datanode viewer => scenario)

[github-actions[bot]]

Coverage report for gui

St.:grey_question:	Category	Percentage	Covered / Total
🟢	Statements	80.46%	2224/2764
🟡	Branches	61.84%	1345/2175
🟡	Functions	74.95%	389/519
🟢	Lines	80.86%	2062/2550

Test suite run success

317 tests passing in 35 suites.

Report generated by 🧪jest coverage report action from 45bf8c6ae58e46ea601f374d11f0062f9d5836b9

[github-actions[bot]]

☂️ Python Coverage

current status: ✅

Overall Coverage

Lines	Covered	Coverage	Threshold	Status
5197	4479	86%	85%	🟢

New Files

No new covered files...

Modified Files

File	Coverage	Status
src/taipy/gui/_renderers/builder.py	83%	🟢
src/taipy/gui/gui.py	90%	🟢
TOTAL	87%	🟢

updated for commit: 45bf8c6 by action🐍