fix: 修复 h5 picker 的 mode="date" 且 fields="year" 时，start 和 end 属性为默认值报类型错误的问题 fixed #1687

src/platforms/h5/view/components/picker/index.vue

@@ -79,7 +79,7 @@ function getDefaultStartValue () {
     const year = new Date().getFullYear() - 100
     switch (this.fields) {
       case fields.YEAR:
-        return year
+        return year.toString()
       case fields.MONTH:
         return year + '-01'
       case fields.DAY:
@@ -97,7 +97,7 @@ function getDefaultEndValue () {
     const year = new Date().getFullYear() + 100
     switch (this.fields) {
       case fields.YEAR:
-        return year
+        return year.toString()
       case fields.MONTH:
         return year + '-12'
       case fields.DAY: