Allow a project import URL to be blank to prevent false positives

app/models/project.rb

@@ -162,7 +162,7 @@ class Project < ActiveRecord::Base
   validates :namespace, presence: true
   validates_uniqueness_of :name, scope: :namespace_id
   validates_uniqueness_of :path, scope: :namespace_id
-  validates :import_url, addressable_url: true, if: :import_url
+  validates :import_url, addressable_url: true, if: "import_url.present?"
   validates :star_count, numericality: { greater_than_or_equal_to: 0 }
   validate :check_limit, on: :create
   validate :avatar_type,
@@ -482,7 +482,7 @@ class Project < ActiveRecord::Base
   end
 
   def create_or_update_import_data(data: nil, credentials: nil)
-    return unless valid_import_url?
+    return unless import_url.present? && valid_import_url?
 
     project_import_data = import_data || build_import_data
     if data

spec/models/project_spec.rb

@@ -142,10 +142,10 @@ describe Project, models: true do
       expect(project2).to be_valid
     end
 
-    it 'does not allow to introduce an empty URI' do
+    it 'allows an empty URI' do
       project2 = build(:project, import_url: '')
 
-      expect(project2).not_to be_valid
+      expect(project2).to be_valid
     end
 
     it 'does not produce import data on an empty URI' do