Target filename for media conversion must not be the same as source filename.

[Lewis Rosenthal]

Selecting an existing JPG to convert to a JPG of the same name results in the source file being overwritten with a black image (not a blank image, but an image of the same size, rendering all black).

While a reasonable argument could be made that the source and target type should not be allowed to be identical (JPG -> JPG), this does produce valid results (though not compared for fidelity). The issue in this ticket arises when the target overwrites the source.

The thumbnail view in the light table remains unchanged, but the image itself is sullied (though apparently a valid JPG), and attempting to convert again yields a black preview box at the top of the conversion dialog.