A few parts in the code check for a variable being null, then execute some code.
However, when using Parameters, the value itself won't be null, but if that parameter then expands to an empty string it would be equivalent of null.
For example: In
https://github.com/jenkinsci/hockeyapp-plugin/blob/master/src/main/java/hockeyapp/HockeyappRecorder.java#L216

Checking dsymPath for null would return "$SYMBOLEFILES" as not null; however, if a build is parameterized and that value is empty, it would be equivalent of null when expanded on line 217/218

Therefore, should be expanded before checking.