[TemplateProcessor] Fix 0 considered as empty string

[cavasinf]

Description

Fixes #2572

Checklist:

• My CI is 🟢
• I have covered by unit tests my new code (check build/coverage for coverage report)
• I have updated the documentation to describe the changes
• I have updated the changelog

[coveralls]

coverage: 96.918%. remained the same
when pulling c6a9569 on cavasinf:patch-1
into feadceb on PHPOffice:master.

[adriansuter]

👍 Ready to be merged.

[Progi1984]

@cavasinf Could you update the changelog, please ?

[dsuurlant]

We are running into this issue and it would be great to see this fix merged!

[cavasinf]

Sorry for the delay!
@Progi1984 I've added it to the BC Breaks part, as it will certainly change the behavior on other devs processor result.

[supernova-ws]

Sorry for the delay! @Progi1984 I've added it to the BC Breaks part, as it will certainly change the behavior on other devs processor result.

Hi! Is there any plan to merge it to main repo?

Thanks for a great library!

[4RSIM3R]

so, when it will be merged?