[REG 4.3->4.4] Locator doesn't list project files when there are matching open files

Very easily reproducible:

• Open the Qt Creator project
• Close all files
• Trigger the locator
• Type c (without space). All the files that contain 'c' appear
• Open any of them
• Type c again - only the open file appears
• Type k. All the files with k appear (unless the file you opened contains 'k')