.qrc file disappears when changing extension

1. Create a new project of type "Qt Quick Application - Empty".
   You'll have to choose the minimal required Qt version "5.10".
2. Configure the project to use a kit with Qt 5.10.1.
3. In the Projects view, right-click on the project's .qrc-file and select "Rename..." from the context menu.
4. Change the file's extension to ".QRC", i.e. capitalize the letters.
   After the project was parsed again, the file will disappear from the project tree completely. It will not move to "Other files".

After renaming, the file should still be listed in the project tree. With kits using newer versions of Qt, this seems to work correctly.

Found when updating Squish test tst_rename_file.