When a hoster server replies with a body that JSON-parses to a
non-object (literal "null", a bare string, a number, a top-level
array), uploadFile's downstream code crashed:
payload.msg → TypeError on null
payload.status → TypeError on null
config.parseResult() → TypeError inside parseDoodstreamResult
(payload.result) and parseByseResult
(payload.files / payload.result)
The user saw a confusing "Cannot read properties of null" instead of
a useful "server returned no JSON object". Found by deep-audit pass.
Fix in three places:
1. uploadFile (lib/hosters.js): after JSON.parse, normalise non-object
payloads to {}. Subsequent `payload.X` accesses then return
undefined and the existing fallback paths handle the empty case.
2. parseDoodstreamResult: defensive `payload && payload.result` so
direct callers (tests, hypothetical future callers) get the same
guarantee instead of relying on uploadFile to have normalised.
3. parseByseResult: same `payload || typeof payload !== 'object'`
short-circuit at entry, plus null-checks on `f` (the first files
entry) so a server returning [null] in files doesn't crash either.
Tests: 7 new unit tests covering null/undefined/string/number/array
payloads, malformed files entries, the fileRejected/accountError
classification (regression-pinning the 3.1.4 phrasing tweaks), and
the valid-filecode happy path. 126/126 green.
