[3] Fix Undefined class RuntimeException

[PhilETaylor]

Code review.

This is a namespaced file, and therefore any reference to RuntimeException needs to be namespaced back to the root.

[joomdonation]

I have tested this item ✅ successfully on a15f0dd

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[Quy]

I have tested this item ✅ successfully on a15f0dd

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_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/34331.}

[Quy]

RTC

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_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/34331.}

[bembelimen]

Thanks

[laoneo]

This is not on milestone 4.

[bembelimen]

Right, was too much Joomla! 4 stuff today

[zero-24]

But it needs the 3.9 milestone ;-)