normalize license to remove blank strings

app/models/model.rb

@@ -19,6 +19,10 @@ class Model < ApplicationRecord
   before_validation :strip_separators_from_path, if: :path_changed?
   before_validation :slugify_name, if: :name_changed?
 
+  before_validation :normalize_license
+  # In Rails 7.1 we will be able to do this instead:
+  # normalizes :license, with: -> license { license.blank? ? nil : license }
+
   attr_reader :organize
   def organize=(value)
     @organize = ActiveRecord::Type::Boolean.new.cast(value)
@@ -105,6 +109,10 @@ def new?
 
   private
 
+  def normalize_license
+    self.license = nil if license.blank?
+  end
+
   def strip_separators_from_path
     self.path = path&.trim_path_separators
   end

spec/models/model_spec.rb

@@ -54,6 +54,12 @@
       m.license = nil
       expect(m).to be_valid
     end
+
+    it "normalizes blank licenses to nil" do
+      m = build(:model, license: "")
+      m.validate
+      expect(m.license).to be_nil
+    end
   end
 
   it "strips leading and trailing separators from paths" do