[Fix] F-PROT Antivirus: only check return code to determine infection

[Fix] F-PROT Antivirus: only check return code to determine infection

F-PROT Antivirus uses return codes 1-3 (infected, suspicious, both) to signal an infection, while 4-255 are various error codes (including infected files were found before the error occured, but it's too complicated to handle all that edge case scenarios).