reporting: make errors more clear

matlab/reporting/@elements/elements.m

matlab/reporting/@elements/subsasgn.m

matlab/reporting/@elements/subsref.m

matlab/reporting/@graph/createGraph.m

matlab/reporting/@graph/graph.m

matlab/reporting/@graph/subsasgn.m

matlab/reporting/@graph/subsref.m

matlab/reporting/@objArray/getObjs.m

matlab/reporting/@objArray/objArray.m

matlab/reporting/@objArray/subsasgn.m

matlab/reporting/@objArray/subsref.m

matlab/reporting/@page/page.m

matlab/reporting/@page/subsasgn.m

matlab/reporting/@page/subsref.m

matlab/reporting/@pages/pages.m

matlab/reporting/@pages/subsasgn.m

matlab/reporting/@pages/subsref.m

matlab/reporting/@report/report.m

matlab/reporting/@report/subsasgn.m

matlab/reporting/@report/subsref.m