Improve error message when associations are not defined.
Improve error message when associations are not defined.

ADmad/cakephp,tenkoma/cakephp,garethellis36/cakephp,davidyell/cakephp,mvdriel/cakephp,cakephp/cakephp,CakeDC/cakephp,petteyg/cakephp,mvdriel/cakephp,tenkoma/cakephp,CakeDC/cakephp,tenkoma/cakephp,mvdriel/cakephp,garethellis36/cakephp,ADmad/cakephp,ADmad/cakephp,petteyg/cakephp,CakeDC/cakephp,davidyell/cakephp,cakephp/cakephp,tenkoma/cakephp,mvdriel/cakephp,CakeDC/cakephp,davidyell/cakephp,garethellis36/cakephp,cakephp/cakephp,ndm2/cakephp,dakota/cakephp,ndm2/cakephp,petteyg/cakephp,ndm2/cakephp,garethellis36/cakephp,petteyg/cakephp,dakota/cakephp,ADmad/cakephp,cakephp/cakephp,dakota/cakephp,dakota/cakephp,ndm2/cakephp