Fixed `(null)` references

lib/cocoapods/installer/user_project_integrator.rb

@@ -118,6 +118,8 @@ module Pod
         
         # TODO: Remove the file_refs in Pods/Resources if they are not linked
         #       to any native_target anymore (which can happen after a target deintegration)
+
+        # TODO: Remove the Pods/Resources group if empty
       end
 
       # Warns the user if the podfile is empty.

lib/cocoapods/installer/user_project_integrator/target_integrator.rb

@@ -213,9 +213,6 @@ module Pod
               user_target.resources_build_phase.remove_file_reference(file_ref)
             end
           end
-          # Remove the group and its children
-          resources_group.remove_children_recursively
-          resources_group.remove_from_project
           true
         end