--assert-body-eq "" can never pass

[korya]

Problem

AssertBodyEqual short-circuits on an empty body before comparing:

if len(res.BodyBytes) == 0 {
    return fmt.Errorf("body: expected %q, missing", expContent)
}

So asserting that a body equals the empty string always fails — and the error message is self-refuting.

Reproduction

$ http-assert --assert-body-eq '' http://127.0.0.1:8791/empty    # 204, empty body
[:] HTTP/1.1 204 No Content
- body: expected "", missing
[exit=93]

Related

AssertBodyMatch has the same shape: a pattern that legitimately matches the empty string (e.g. ^$) can never pass.

Affected code

assertions.go — AssertBodyEqual, AssertBodyMatch

Suggested fix

Drop the special-case and compare directly. The "missing" guard only exists to produce a nicer message; it should not change the verdict.