Fail to compile when extending JPanel when -Yexplicit-nulls is enabled

[rcano]

Minimized code

object Crash {
  class Foo extends javax.swing.JPanel
}

Output (click arrow to expand)

 Found:    Array[("DebugGraphics.NONE_OPTION" : String) | 
   ("DebugGraphics.LOG_OPTION" : String)
  ("DebugGraphics.FLASH_OPTION" : String) | 
   ("DebugGraphics.BUFFERED_OPTION" : String)
 ]
 Required: Array[String | UncheckedNull] | UncheckedNull

Expected

it should compile without errors.

[noti0na1]

This has been fixed in #9884.