Empty files are not overwritten with non-empty ones

[ale-rinaldi]

Hello,

first of all, thanks for this script, it's really useful in my workflow.

I noticed an issue where empty (zero-byte) files are never overwritten with non-empty files.

Steps to reproduce

# Create an empty file
$ touch empty-file.txt
# Create a non-empty file
$ echo "Some text" > non-empty-file.txt
# Upload the empty file
$ ./dropbox_uploader.sh upload empty-file.txt /Temp/test.txt
 > Uploading "/home/dropbox/empty-file.txt" to "/Temp/test.txt"... DONE
# Upload the non-empty file trying to overwrite the empty one
$ ./dropbox_uploader.sh upload non-empty-file.txt /Temp/test.txt
 > Skipping file "/home/dropbox/non-empty-file.txt", file exists with the same hash

What should happen

The second file, different from the first, empty one, is uploaded and overwrites the empty one

What actually happens

The upload is skipped because the files are considered identical