Fix NoMethodError when Mongoid's raise_not_found_error is false

Fixes #2623

Author: mshibuya

lib/rails_admin/adapters/mongoid.rb

@@ -19,7 +19,9 @@ def new(params = {})
       end
 
       def get(id)
-        AbstractObject.new(model.find(id))
+        object = model.find(id)
+        return nil unless object
+        AbstractObject.new(object)
       rescue => e
         raise e if %w(
           Mongoid::Errors::DocumentNotFound

spec/rails_admin/adapters/mongoid_spec.rb

@@ -39,6 +39,14 @@
       expect(@abstract_model.get('4f4f0824dcf2315093000000')).to be_nil
     end
 
+    context 'when Mongoid.raise_not_found_error is false' do
+      before { allow(Mongoid).to receive(:raise_not_found_error).and_return(false) }
+
+      it '#get returns nil when id does not exist' do
+        expect(@abstract_model.get('4f4f0824dcf2315093000000')).to be_nil
+      end
+    end
+
     it '#first returns a player' do
       expect(@players).to include @abstract_model.first
     end