Issue 94 File thumbnails don't show up after upload of new files

[sunilnatraj]

Issue - 94
Media preview fails to load in case of new data as the newly added data do not contain the prefix "File:".
Updated code to handle the scenario of missing prefix "Fiile:"

[sunilnatraj]

@wetneb Please review

[wetneb]

Thanks! It's curious that there is this discrepancy. It would probably be worth adjusting the upload code so that it adds the File: prefix to the uploaded files, so that existing and uploaded files are reprersented in the same way in the grid.

[wetneb]

Note: I haven't tested this yet, I might have an occasion this week-end to try it out. Leaving it open also for @sebastian-berlin-wmse to have the opportunity to chime in.

[sunilnatraj]

Thanks! It's curious that there is this discrepancy. It would probably be worth adjusting the upload code so that it adds the File: prefix to the uploaded files, so that existing and uploaded files are reprersented in the same way in the grid.
@wetneb In case of new data as post upload the local data is not updated there is the discrepancy in file property. We cannot add the prefix in the new data as that will break the file validation rule - "file cannot have special character :"

[wetneb]

I have opened OpenRefine/OpenRefine#6996 about this.

I do not mean that the user should add the File: prefix themselves. I mean that OpenRefine itself should add the File: prefix when changing the cells reconciled to "New" to cells reconciled to the newly-created files.

[sunilnatraj]

@wetneb Can this PR be merged?