Added failing test for #2209
Merge branch 'master'
Fixes #2209: When I18N message translation is missing source language is now used for formatting
Added assignment back. See https://github.com/yiisoft/yii2/pull/2285#discussion_r9566711
Merge pull request #2285 from yiisoft/missing-translation-formatting

When translation is missing source language should be used for formatting