Complicate with less 3

Fix #7850

components/style/color/bezierEasing.less

@@ -100,6 +100,8 @@
   };
 
   this.colorEasing = BezierEasing(0.26, 0.09, 0.37, 0.18);
+  // less 3 requires a return
+  return '';
 })()`;
 }
 // It is hacky way to make this function will be compiled preferentially by less