getSolutions with errors overload is broken

Issue #70 resolved
Former user created an issue

https://bitbucket.org/traclabs/trac_ik/src/3ae73f0e7e1e7cb26560cb6c10563b4dce805fa0/trac_ik_lib/include/trac_ik/trac_ik.hpp#lines-79

it is passing the member variable "solutions" not the argument "solutions_", thus no solutions are passed back.