GCC sanitizer reports incorrect downcast error in Awl/SingleList.h

[dmitriano]

GCC with -fsanitize=undefined reports the following:

Awl/SingleList.h:250:23: runtime error: downcast of address 0x000002a33fe0 which does not point to an object of type 'Observer'
0x000002a33fe0: note: object has invalid vptr
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
^~~~~~~~~~~~~~~~~~~~~~~
invalid vptr

in function:

T * null() { return (T *)&Null; }

[dmitriano]

resolved in master branch