Error checking is now more strict; work around unreliability in tests
as failure/success depends on libshout configuration

Gentle reminder by AddressSanitizer.

Simple copy+paste mistake.

For example, this solves the combination of an explicit format string
'@a@ - @t@' in combination with an MP3 input file that lacks either
artist or title

Found by Coverity

Regression found and reported by zygmund2000 on Github

Fixes a segfault when there is a typo in the <encoder /> setting.

It's no longer relevant.

This reverts commit b0ef65fc.
It's been nicer to read before, and static analysis can ignore this one.