FunctionCx: Fix FunctionCx initialization in trans_fn()
FunctionCx: Fix FunctionCx initialization in trans_fn()

graydon/rust,aidancully/rust,graydon/rust,graydon/rust,graydon/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust,aidancully/rust,aidancully/rust,aidancully/rust