去掉analyze 出现的警告

PNPieChart.m:137:33: warning: Passed-by-value struct argument contains
uninitialized data (e.g., via the field chain: 'origin.x')
get rid of the warning form analyzing

PNPieChart.m:137:33: warning: Passed-by-value struct argument contains
uninitialized data (e.g., via the field chain: 'origin.x')