fix: datePicker support empty, close #6510

Author: tangjinzhou

components/vc-picker/RangePicker.tsx

@@ -315,7 +315,11 @@ function RangerPicker<DateType>() {
 
           // Fill disabled unit
           for (let i = 0; i < 2; i += 1) {
-            if (mergedDisabled.value[i] && !getValue(postValues, i) && !getValue(props.allowEmpty, i)) {
+            if (
+              mergedDisabled.value[i] &&
+              !getValue(postValues, i) &&
+              !getValue(props.allowEmpty, i)
+            ) {
               postValues = updateValues(postValues, props.generateConfig.getNow(), i);
             }
           }

components/vc-picker/generate/dayjs.ts

@@ -123,6 +123,7 @@ function findTargetStr(val: string, index: number, segmentation: string) {
 }
 
 const toDateWithValueFormat = (val: string | Dayjs, valueFormat: string) => {
+  if (!val) return null;
   if (dayjs.isDayjs(val)) {
     return val;
   }