pluginsupdate.pl: Exception handling if pre-/release file is not a valid ini file
pluginsupdate.pl: Exception handling if pre-/release file is not a valid ini file

Fixes #1110

mschlenstedt/Loxberry,mschlenstedt/Loxberry,mschlenstedt/Loxberry,mschlenstedt/Loxberry,mschlenstedt/Loxberry,mschlenstedt/Loxberry