Disable "From Current Palette" preset option when creating a new pale…

…tte, if there is no current palette

Fixes #659

src/Autoload/Palettes.gd

@@ -119,6 +119,8 @@ func _create_new_empty_palette(name: String, comment: String, width: int, height
 
 
 func _create_new_palette_from_current_palette(name: String, comment: String) -> void:
+	if !current_palette:
+		return
 	var new_palette: Palette = current_palette.duplicate()
 	new_palette.name = name
 	new_palette.comment = comment

src/Palette/CreatePaletteDialog.gd

@@ -35,6 +35,9 @@ func open(opened_current_palette: Palette) -> void:
 	# Disable ok button until user enters name
 	toggle_ok_button_disability(true)
 
+	# Disable create "From Current Palette" if there's no palette
+	preset_input.set_item_disabled(1, !current_palette)
+
 	# Stop all inputs in the rest of the app
 	Global.dialog_open(true)
 	popup_centered()