fix failure of test_remove_issue_watcher_from_sidebar at UI IssuesTest
<pre> 2) Failure: test_remove_issue_watcher_from_sidebar(Redmine::UiTest::IssuesTest) [test/ui/issues_test.rb:186]: "Watcher.count" didn't change by -1. <3> expected but was <4>. </pre>
Authored by: tmaruyama 2013-05-09
Parent: [r11806]
Child: [r11808]
