AutocompleteLinesController: Don't error if no `q` param is passed

Previously the action would respond with a 500 error if no `q` parameter
was given in the request. Instead, respond with a 200 and fix the error
that occurs as a result of assuming that `params[:q]` exists in
`AutocompleteLinesController#collection`.

Refs #5889

1 files changed, 8 insertions, 0 deletions

diff --git a/spec/controllers/autocomplete_lines_controller_spec.rb b/spec/controllers/autocomplete_lines_controller_spec.rb
index d52cecd04..60dff5381 100644
--- a/spec/controllers/autocomplete_lines_controller_spec.rb
+++ b/spec/controllers/autocomplete_lines_controller_spec.rb
@@ -63,5 +63,13 @@ RSpec.describe AutocompleteLinesController, type: :controller do
 
       expect(assigns(:lines).to_a).to eq([line])
     end
+
+    it "doesn't error when no `q` is sent" do
+      get :index,
+        referential_id: referential.id
+
+      expect(assigns(:lines).to_a).to be_empty
+      expect(response).to be_success
+    end
   end
 end