This Bugzilla instance is a read-only archive of historic NetBeans bug reports. To report a bug in NetBeans please follow the project's instructions for reporting issues.
This is only a cosmetic issue. The font property value in properties window is not antialised when it's value is null. It doesn't look so bad, when some font is set, because the field is used as "font preview" and so the displayed value uses completely different font. See issue 149052 for screenshot and more comments.
Font editor in Form module does the painting.