hero animation throws errors on navigation

[aqandrew]

1. when clicking to a subpage from the homepage, the setInterval for changing hero text colors still runs:

   (index):46 Uncaught TypeError: Cannot read properties of null (reading 'style')
   at (index):46:16
   at Array.forEach (<anonymous>)
   at setGradientColorCustomProperties ((index):45:16)
   at activateMagicGradient ((index):63:5)
   

2. when clicking back to the homepage from a subpage, registerProperty tries to re-register color properties:

   VM337:26 Uncaught DOMException: Failed to execute 'registerProperty' on 'CSS': The name provided has already been registered.
   at <anonymous>:26:9
   at Array.forEach (<anonymous>)