The code tried hard to ignore garbage URLs, as Qt is quite lenient, e.g. QUrl("Garbage Url") is still valid.
There is no way to change the strictness of a QUrl after creation,
so the code would enforce it by doing QUrl strictUrl(inputUrl.toString(), QUrl::StrictMode).
However, toString() defaults to PrettyDecoded which avoids percent-encoding and keeps spaces
in tact which is not a valid thing to have in a strict URL.
Effectively, we want to ensure a URL is either a valid path to a local file,
or one of the special applications (for menu ids), or preferred for preferred applications, like web browser,

BUG: 385727
FIXED-IN: 5.18.0

Differential Revision: https://phabricator.kde.org/D26941