Fix config.value to allow 0 numeric value

[AndreaPaciolla]

I'm submitting a

[X] Bug / Regression
[ ] Feature Request / Proposal
[ ] Question

I'm using

NG Dynamic Forms Version: `X.Y.Z`

[ ] Basic UI
[ ] Bootstrap UI  
[ ] Foundation UI
[ ] Ionic UI
[ ] Kendo UI
[ ] Material  
[ ] NG Bootstrap
[X] Prime NG

Description

When config.value is equals to 0, condition config.value || null got evaluated as null so no 0 value can be passed.
The fix allows 0 to be evaluated correctly.

[udos86]

@AndreaPaciolla Thanks!

Your PR has been merged and will be released in 5.4.6.