I've spotted a typo (of no real consequence) in images/bitmap.h:
#ifndef REACTRION_REACTION_H
It's definitely my BitMap object which isn't being created, so I'm missing something:
(2.551870) amiga/gui.c ami_gui_splash_open 5189: WindowBase = 0x5be15860
(2.642908) amiga/gui.c ami_gui_splash_open 5190: WindowObject = 0x539a7ba4
(2.712036) amiga/gui.c ami_gui_splash_open 5191: BitMapBase = 0x579b52c0
(2.784028) amiga/gui.c ami_gui_splash_open 5192: BitMapObject = 0x000000
The creation code is this:
struct Screen *wbscreen = LockPubScreen("Workbench");
BitMapObject,
BITMAP_SourceFile, "PROGDIR:Resources/splash.png",
BITMAP_Screen, wbscreen,
BITMAP_Precision, PRECISION_IMAGE,
#ifndef __amigaos4__
BITMAP_Width, 400,
BITMAP_Height, 250,
#endif
BitMapEnd,