Fixes #32474

app/models/user.rb

@@ -351,7 +351,9 @@ class User < ActiveRecord::Base
 
     def find_by_full_path(path, follow_redirects: false)
       namespace = Namespace.find_by_full_path(path, follow_redirects: follow_redirects)
-      namespace&.owner
+      return unless namespace && namespace.kind == 'user'
+
+      namespace.owner
     end
 
     def reference_prefix

spec/models/user_spec.rb

@@ -929,10 +929,20 @@ describe User, models: true do
     end
 
     context 'with a group route matching the given path' do
-      let!(:group) { create(:group, path: 'group_path') }
+      context 'when the group namespace has an owner_id (legacy data)' do
+        let!(:group) { create(:group, path: 'group_path', owner: user) }
 
-      it 'returns nil' do
-        expect(User.find_by_full_path('group_path')).to eq(nil)
+        it 'returns nil' do
+          expect(User.find_by_full_path('group_path')).to eq(nil)
+        end
+      end
+
+      context 'when the group namespace does not have an owner_id' do
+        let!(:group) { create(:group, path: 'group_path') }
+
+        it 'returns nil' do
+          expect(User.find_by_full_path('group_path')).to eq(nil)
+        end
       end
     end
   end