fix(sector): set `arc` as 0 if `startAngle` equals `endAngle`, skip the normalization. - fix apache/echarts#14074. sector blink issue when zero data exists.
fix(sector): set `arc` as 0 if `startAngle` equals `endAngle`, skip the normalization.
- fix apache/echarts#14074. sector blink issue when zero data exists.

ecomfe/zrender,ecomfe/zrender,ecomfe/zrender