fix bug when/after adding row to current database

closes #266 (closed)

• Fix bug adding new row and selecting a plot type for that new row caused by trying to retrieve param from a non-existing row.
• Since now we will have all value color string filled up in database, the empty one should be allow in ValueColorEdit. So this MR will fill value color string when a new plot type is select for a new row.
• Fix bug happen when checking to disable "Reset to org." DB button for the row that has no backup row.
• Fill up empty valueColors in database with default ones: update_default_color.txt