Hello PlantUML,
We observe a 'NullPointerException' when you declare note style just before note, on sequence diagram:
@startuml
a->b
<style>
note {
BackGroundColor green
}
</style>
note over a: note\nover a
@enduml
That is OK, if style is on the beginning:
@startuml
<style>
note {
BackGroundColor green
}
</style>
a->b
note over a: note\nover a
@enduml
That for your support,
Regards,
Th.