V1.6.7 unstable

• Fix: remove build option jdk.gtk.version since the JavaFX 21 does no longer support GTK 2.
• Fix: suggestion list of input helper is not in the appropriate position when there are too many items in it.
• Fix: escape from suggestion mode by ESC key does not work on Linux.
• Fix: exception when close all tabs with markdown or plantuml file opened but never loaded.