fix: date column missing placeholde

packages/nc-gui/components/cell/DatePicker.vue

@@ -83,7 +83,7 @@ watch(
 )
 
 const placeholder = computed(() => {
-  if (isEditColumn.value && modelValue === null) {
+  if (isEditColumn.value && ( modelValue === '' || modelValue === null )) {
     return '(Optional)'
   } else if (modelValue === null && showNull.value) {
     return 'NULL'

packages/nc-gui/components/cell/DateTimePicker.vue

@@ -136,7 +136,7 @@ watch(
 )
 
 const placeholder = computed(() => {
-  if (isEditColumn.value && modelValue === null) {
+  if (isEditColumn.value && ( modelValue === '' || modelValue === null )) {
     return '(Optional)'
   } else if (modelValue === null && showNull.value) {
     return 'NULL'

packages/nc-gui/components/cell/TimePicker.vue

@@ -88,7 +88,7 @@ watch(
 )
 
 const placeholder = computed(() => {
-  if (isEditColumn.value && modelValue === null) {
+  if (isEditColumn.value && ( modelValue === '' || modelValue === null )) {
     return '(Optional)'
   } else if (modelValue === null && showNull.value) {
     return 'NULL'

packages/nc-gui/components/cell/YearPicker.vue

@@ -75,8 +75,8 @@ watch(
 )
 
 const placeholder = computed(() => {
-  if (isEditColumn.value && modelValue === null) {
-    return 'Select default year (Optional)'
+  if (isEditColumn.value && ( modelValue === '' || modelValue === null )) {
+    return '(Optional)'
   } else if (modelValue === null && showNull.value) {
     return 'NULL'
   } else if (isYearInvalid.value) {