lass: fix reverb use-after-free in ConstructorCommon

[passyur]

Problem

Renders that apply reverb crash with a SIGSEGV on the first reverb call.

Root cause

Reverb::ConstructorCommon's first parameter was named percentReverb, which shadows the member of the same name. So:

Envelope* temp = new Envelope(*percentReverb);
delete percentReverb;
percentReverb = temp;   // updates the LOCAL parameter, never this->percentReverb

• For the default / room-size constructors, the member was set before the call, then freed via the parameter alias and never reassigned → dangling.
• For the Envelope* constructors, the constructor's own parameter also shadows the member, so they relied on ConstructorCommon to set it — which it never did → uninitialised.

Either way, the first reverb call does new Envelope(*percentReverb) on a bad pointer (and deletes it again), i.e. a use-after-free + double-free.

Fix

Assign this->percentReverb in ConstructorCommon (parameter renamed to percentReverbInput to remove the shadowing). This is the clearly intended behaviour — a private owned copy of the mix envelope.

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