Adding exception type for empty callback functions#301

gregmedd wants to merge 4 commits intoeclipse-uprotocol:v1.0_up-v1.6.0eclipse-uprotocol/up-cpp:v1.0_up-v1.6.0from

gregmedd:bugfix/1.0.2/194-std-function-checksgregmedd/up-cpp:bugfix/1.0.2/194-std-function-checksCopy head branch name to clipboard