usermem-z80-thunked: Fix crash if we uzero exactly one byte

diff --git a/Kernel/usermem_std-z80-thunked.s b/Kernel/usermem_std-z80-thunked.s
index 65dd9e5..2e74362 100644 (file)
--- a/Kernel/usermem_std-z80-thunked.s
+++ b/Kernel/usermem_std-z80-thunked.s
@@ -184,7 +184,7 @@ zeroit:
        dec bc
        ld a,b
        or c
-       ret z
+       jp z, map_kernel_low
        ld e,l
        ld d,h
        inc de