How do I create a flow that checks if a date column is blank, if it is blank it needs to use a default date to create reminders

[maily]

Hi community. 
I have created a reminder flow that runs everyday to check if the current day is the same as the valid until date if the dates are the same, it should send out an reminder.  

I have created two columns: 
Valid until date : Selected by the document owner, if they have a specific date.
Default Valid Date = Default date, adding 1 year to the last modified date.

Valid until date (Date) : If this column has a date the flow should calculate the reminder days and send out the reminder if the date is equals to the current date.

Valid until date (0) : If the column is blank, the flow should use the default valid date column. 

I have an issue creating the condition to check if the valid date has been selected, I cannot make it switch to the no branch if the valid until column is blank. So the flow keeps failing because the column is blank. 

The first sceenshot shows a test where I added a date in the Valid until date. and it was able to send a reminder. 

With the rest of my documents that was supposed to go into the no branche because the valid until date is empty. 
However it goes into the same branch as fails because the flow cannot calculate the reminder dates. 

Thank you in advance for your help!

[grantjenkins · Accepted solution]

That's a long name for your Apply to each 😉

You might need to check if the date is null. See the Condition below. The expression I've used is:

items('Send_reminders_to_Document_Owner_based_on_Valid_until_date')?['Valid until date']

null

Note that I've used a question mark ? in the expressions to set the value to null if it doesn't find the property.

[Sundeep_Malik · Accepted solution]

Hey @maily 

I was stuck in a similar situation some days back.

So, for the null date you can make a condition such that if the date is null take the default date, and if the date is not null take the original date. So, the condition should like this:

if( equals(datefield,''),'default date', 'original date field')

So, by above expression, I am checking if date field is null or not, if it is I am taking the default date and if it not null I am taking the original date.