Fix issue for `subjects#form`

app/components/subject_index_form_component.rb

@@ -4,10 +4,12 @@ class SubjectIndexFormComponent < BaseComponent
 	def initialize(current_user:, subject_index:, opts:)
 		@subject_index = subject_index
 		@opts = opts
-		@parent_id = @opts[:parent_id]
+		@parent_id = opts[:parent_id]
 	end
 
 	def parent
+		return if parent_id.blank?
+
 		Cdao::Subject.find(parent_id)
 	end
 

app/components/subject_index_form_component/subject_index_form_component.html.erb

@@ -11,8 +11,10 @@
 		<div cass="row">
 			<div class="col-sm-12">
 				<strong> <%= label_tag :subjects %> </strong>
-				<select class="form-control subjects-selectize ps-0 pe-0" name="parent_id" id="parent_id" value="<%= parent_id %>">
+				<select class="form-control subjects-selectize ps-0 pe-0" name="parent_id" id="parent_id">
-					<option value="<%= parent_id %>" selected="selected"> <%= parent.name %> </option>
+					<% if parent_id.present? %>
+						<option value="<%= parent_id %>" selected="selected"> <%= parent.name %> </option>
+					<% end %>
 				</select>
 			</div>
 		</div>