Resolve "[CLANG18] MSAN: use-of-uninitialized-value in lib_com/tools_fx.c:1487:16"

• Related issues: #2326 (closed)
• Requested reviewers: @kiene @tamarapu (maybe also @vaclav )

Reason why this change is needed

• There was MSAN error which points to a case of using L_FRAME48k. Looking at the code, there seems to be multiple places in function renderInputMasa where this is done and also scaling of input is done for too many channels (in one case even up to number of output channels).

Description of the change

• Attempt to fix the scaling to apply only to actual input samples.

Affected operating points

• This should be BE.

Closes #2326 (closed)