Backport rescue in Project#import_url from EE

EE added a `rescue` to the method Project#import_url, which could cause
merge conflicts when changing this method. This commit backports those
changes to CE, reducing the chances of running into a merge conflict.

app/models/project.rb

@@ -688,6 +688,8 @@ class Project < ActiveRecord::Base
     else
       super
     end
+  rescue
+    super
   end
 
   def valid_import_url?