Sending a file again appends file to existing. Result is data corruption

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**Describe the bug**
A clear and concise description of what the bug is.

If I send a file to tus-php, and then send the same file again, it appends the a second copy of the file to the end of the first uploaded copy.

**To Reproduce**
Steps to reproduce the behavior:
1. Upload a file, EG: "myfile.txt".
2. Upload the same file again.
3. In my upload folder, "myfile.txt" is now 2x as long as original.

**Expected behavior**
A clear and concise description of what you expected to happen.
At step 2, I should receive a link to the file instead of a "starting at 0" response.

**Screenshots**
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**Additional context**
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