Repeatedly adding file extensions in disk creation

[tarix29]

In the "Create Virtual Hard Disk" dialog during the creation of a new virtual machine in expert mode, selecting any of the hard disk file type options adds an extra extension to the name of the file. For example, if "VDI (Virtual Disk Image)" is selected and the file location displays "C:/Users/user/VirtualBox VMs/os/disk.vdi", and the user then selects "VHD (Virtual Hard Disk)" then the file location is changed to "C:/Users/user/VirtualBox VMs/os/disk.vdi.vhd" instead of "C:/Users/user/VirtualBox VMs/os/disk.vhd". Repeated switching back and forth between the two will yield "C:/Users/user/VirtualBox VMs/os/disk.vdi.vhd.vdi.vhd.vdi.vhd". Note that the bug also occurs while switching between the other options.

This error occurs during hard disk creation during the creation of a new VM, or by creating a new hard disk in the settings dialogue of an existing VM. This only occurs in expert mode in both cases.

Steps to reproduce:

1. Open VirtualBox click the "New" button to create a new VM.
2. Ensure that Expert Mode is selected.
3. Select "Create a virtual hard disk now"
4. Name the VM.
5. Select any operating system type and version, the bug occurs for any of them.
6. Click create.
7. Select a hard disk file type other than the one currently selected e.g. "HDD (Parallels Hard Disk)"
8. Observe that an additional file extension was added to the "File Location" text field.

This bug initially occurred hosted on Windows 10 Version 2004 using a fresh installation of VirtualBox 6.1.10. I was also able to reproduce the error on Xubuntu 18.04 with VirtualBox 6.1.10 following the exact same steps.