Replaced an exception in the initializer of CPXYGraph with a log message and nil return.
Replaced an exception in the initializer of CPXYGraph with a log message and nil return.

--HG--
extra : convert_revision : svn%3A8664401c-e8a0-11dd-9059-71fac19e68c6/trunk%4042

escoz/core-plot,escoz/core-plot,escoz/core-plot,escoz/core-plot,escoz/core-plot