Exported sumfile loses its file extension if filename is changed before saving

[pubct]

This will make the sumfile "non-executable" for a quick double-click hash check, unless the file extension is manually put in, which is a bit inconvenient.

To reproduce,

• Right click a file, select Hashes
• Select .SHA-512(very likely is happening to all algorithms, but I didn't test all) or .hash(corz)
• Select Export
• Change filename in the popup window (I tried with the name t & test)
• Save