Out of bounds access when edid parsing fails

[oliverchang]

On certain configurations the EDID retrieval and parsing seems to fail, leading to create_patched_edid accessing out of bounds indexes on a zero length vector. This causes gamescope to crash on launch.

In my gamescope output I see:

...
drm: Failed to parse edid
...
/usr/include/c++/12.2.1/bits/stl_vector.h:1123: constexpr std::vector<_Tp, _Alloc>::reference std::vector<_Tp, _Alloc>::operator[](size_type) [with _Tp = unsigned char; _Alloc = std::allocator<unsigned char>; reference = unsigned char&; size_type = long unsigned int]: Assertion '__n < this->size()' failed.
(EE) failed to read Wayland events: Connection reset by peer
(EE) failed to read Wayland events: Broken pipe

While an error is logged in the case where parsing fails, this was not handled as edid_data is assumed to contain valid and non-empty data
as it's passed to create_patched_edid.

This points to a potential underlying bug in di_info_parse_edid in libdisplay-info, but it still seems reasonable to guard against parsing errors in general?

The offending input to di_info_parse_edid in libdisplay-info is (base64 encoded):

AP///////wAHIQEBBwYhIDEgAQSlCQ94qrBlplZTnSgMUFQAAAABAQEBAQEBAQEBAQEBAQEBSxog
NjAAIlASEkQEXpcAAAAeKhrQjCAAKFBACKABXpcAAAAeUxFYpCDAGDBECMQAXpcAAAAeAAAA/ABB
WUFORU9XWEdBCiAgAXoCAxAw0FAgAC5QIAqgAXG1LRjQoCCAKEBACIQBXpcAAAAenhYAjDAAOEAw
CqgBXpcAAAAeiw9YoCAgWDA4EIQCXpcAAAAeAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAVg==