UI: Clamp float values possibly representing infinity to integer size

Casting a floating point type to an integer type has undefined behaviour
if the value does not fit into the destination type.

As the volume meter is initialized with floats values representing +inf
(as makes sense for a dB meter), values should be explicitly clamped
to integer boundaries.
This commit is contained in:
Internal Server Error - Gitea: Git with a cup of tea
500 Internal Server Error

Gitea Version: 1.28.0+dev-477-g8b6ad49a5f