This is a known issue with recent versions of the Ren'Py engine. The file is safe and the only solutions available to us right now are either to drop support for 32bit, or wait until antivirus problems begin to recognize these new 32bit executables generated by Ren'Py. You'll have to switch off your antivirus during the download and add an exclusion for Sileo in the meanwhile. Alternatively, try a different antivirus.