Improve error handling in the method calling view controller.
Improve error handling in the method calling view controller.

Show an alert on failure, push or pop on success.
nikhildhamsaniya/Alpha,BrianBatchelder/FLEX,pxpgraphics/Alpha,xNUTs/Alpha,Flipboard/FLEX,pjebs/FLEX,zhaoguohui/FLEX,DaidoujiChen/FLEX,deer-hope/FLEX,hoaquo/FLEX,tttpeng/FLEX,NSExceptional/FLEX,gank0326/FLEX,ramoslin02/FLEX,pxpgraphics/Alpha,xNUTs/Alpha,Legoless/Alpha,Suninus/FLEX,tttpeng/FLEX-DatabaseBrowser,NSExceptional/FLEX,otatime/FLEX,nikhildhamsaniya/Alpha,OdNairy/Alpha,hugo-/FLEX,pxpgraphics/Alpha,fbernardo/FLEX,pocketgems/FLEX,Flipboard/FLEX,erichoracek/FLEX,OdNairy/Alpha,evliu/FLEX,jdk89757/FLEX,msdgwzhy6/FLEX,Automatic/FLEX,iBcker/FLEX,sunfei/FLEX,nanonation/FLEX,xNUTs/Alpha,appspector/FLEX,lintaoSuper/FLEX,Xiaobin0860/FLEX,programming086/FLEX,Kingside/FLEX,Legoless/Alpha,OdNairy/Alpha,1yvT0s/FLEX,nikhildhamsaniya/Alpha