ParameterInput: Add current value to options list

If the current value is not already in the options list, add it to the
list.

https://phabricator.endlessm.com/T35564

Author: dylanmccall

addons/block_code/ui/blocks/utilities/parameter_input/parameter_input.gd

@@ -241,6 +241,18 @@ func _update_option_input(current_value: Variant = null):
 		if item == current_value:
 			selected_item_index = item_index
 
+	if selected_item_index == -1 and current_value:
+		# If the current value is not in the default list of options, add it
+		# and select it.
+		_option_input.add_separator()
+		var item_index = _option_input.item_count
+		var option_label = current_value.capitalize()
+		_option_input.add_item(option_label)
+		_option_input.set_item_metadata(item_index, current_value)
+		selected_item_index = item_index
+	elif selected_item_index == -1:
+		selected_item_index = option_data.selected
+
 	_option_input.select(selected_item_index)