Fix bug in front end "Replace" button

[rbs-jacob]

• [x] I have reviewed the OFRAK contributor guide and attest that this pull request is in accordance with it.

One sentence summary of this PR (This should go in the CHANGELOG!)

Fix bug in frontend "Replace" button. Before it was appending new data instead of replacing it as intended.

Anyone you think should look at this, specifically?

@whyitfor @dannyp303