Throw an interpreter exception when encountering a dynamic expression error.
Throw an interpreter exception when encountering a dynamic expression error.

Without throwing cling cannot communicate to the caller that the code has failed,
as the user code is currently running when failing the dynamic expression evaluation.
Fixes gROOT->ProcessLine("doesNotExist", &res) not signalling any error through res.
Well, it still does not set res to an error - but at least it now throws.

karies/cling,root-mirror/cling,root-mirror/cling,karies/cling,karies/cling,karies/cling,root-mirror/cling,root-mirror/cling,root-mirror/cling,karies/cling,root-mirror/cling,karies/cling