Description:
When editing custom properties in Writer, Click "Add property" and then edit the first one.  After the first one is done, if I click "Add property" again to add the second custom property, the content of the first custom property would disappear.  I need to click "OK" to close the dialog after the first property is done, then relaunch the window by File > Properties again to edit the second one so that the first one would be kept.

Steps to Reproduce:
1. Open File > Properties and choose the Custom Properties
2. Click "Add Property" and edit the first property
3. Click "Add Property" to edit the second property, at the same time the first edited property would be gone.

Actual Results:  
The first edited property was gone.

Expected Results:
It should not clear the previous one and allow users to edit multiple custom properties and then click OK to save once.  I.e., clicking "Add Property" shouldn't clear the previous unsaved properties.


Reproducible: Always


User Profile Reset: No



Additional Info:


User-Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/65.0.3325.146 Safari/537.36