SPI 4 Wire Driver dereferencing a -1 Pointer

[burnin]

While playing around with the library i found a small bug in the code.
I generated code for a ILI9844 display with the "LE SPI 4-Line" + "LE External Controller" Modules.
MPLabX 6.05, XC32 v4.21, GFX library v3.12.2 (Latest).

Bug:
drv_gfx_external_controller.c - DRV_ILI9488_Update() calls GFX_Disp_Intf_Open() from drv_gfx_disp_intf_spi4.c which normally returns a Pointer of type GFX_Disp_Intf.
On failure GFX_Disp_Intf_Open() returns -1.
But the DRV_ILI9488_Update() function checks for 0 (NULL) instead of -1.
Which later results in a data bus exception when the GFX_Disp_Intf_Write() function dereferences the -1 pointer.

Fix:
GFX_Disp_Intf_Open() should return 0 instead of -1 on failure which would be consistent with how invalid pointers are usually handled.

Personal opinion / coding style stuff:
The GFX_Disp_Intf type is typedef'd as a uint32_t which might be why it was confused for a handle instead of a pointer.
So maybe put a void* or uintptr_t there instead of uint32_t so it is 100% clear that this should be a pointer.

[MHGC]

Thanks for the feedback. We will look into this.