After upgrading to 2.5.26, uploading an empty file now ends with: "Error uploading: empty_file.txt"
This was working fine with Struts 2.5.20
Seems the behavior change occurred somewhere in 2.5.22 - 18.104.22.168
For an empty file, seeing org.apache.commons.io.output.ThresholdingOutputStream checking threshold with an "greater than" operator (>),
I guess "fac.setSizeThreshold(0);" does not actually make sure the data is written to a file (hence getting null storeLocation)