The software uses several data sources for a bug report. One such source is your user environment. This is the content of the file
PID is the process ID of a specific process. In the case of a networking program this might reveal to which servers you are connected. Some software allows it to enter a password as commandline option.
Also a hostname can be sensitive. Just assume you are working inside a company. The fact itself that you're working there, could be revealed through a hostname and might be sensitive.
So in many cases a hostname will not sensitive per se, but with additional information it can easily get sensitive or sometimes dangerous.
The error message is just a reminder for you to reflect if your hostname or other information are worth being protected. If no, all is OK. If yes, you should modify the report.