fix unlink-panels test

test/unit/specs/date-picker.spec.js

@@ -1140,10 +1140,10 @@ describe('DatePicker', () => {
         setTimeout(_ => {
           const left = panels[0].querySelector('.el-date-range-picker__header');
           const right = panels[1].querySelector('.is-right .el-date-range-picker__header');
-          const leftText = left.textContent.match(/\d+/g);
-          const rightText = right.textContent.match(/\d+/g);
+          const leftText = left.textContent.match(/\d+/g).map(i => Number(i));
+          const rightText = right.textContent.match(/\d+/g).map(i => Number(i));
 
-          expect(rightText[0] - leftText[0]).to.equal(1);
+          expect((rightText[1] <= 2 ? rightText[0] - 1 : rightText[0]) - leftText[0]).to.equal(1);
           expect((rightText[1] <= 2 ? rightText[1] + 12 : rightText[1]) - leftText[1]).to.equal(2);
 
           done();