I cannot set the display date of a web content structure back to blank after it has changed

Issue

• I am not able to set the display date of a web content structure if it was changed when editing the structure's default value.

Reproduction Steps:

1. Create a web content structure from Content & Data --> Web Content --> Structures
2. Open "Edit Default Values" of the created structure
3. The initial value of "Display Date" is blank (expected behavior)
4. Set "Display Date" to any date and save
5. Open "Edit Default Values" of the created structure again
6. The initial value of "Display Date" is displayed correctly (expected behavior)
7. Remove the "Display Date" to leave it blank and save
8. Open "Edit Default Values" of the created structure again

     Expected result

     The display date is kept blank 
     Actual result
     The Display date shows the last value

Environment

• Liferay DXP 7.4

Resolution

• The issue has been addressed and resolved by LPS-176261. Please upgrade to u66+. 
• There is another related issue where the Display Date in the web content structure is auto-reset to blank. This has been resolved by LPS-175068 from u66.