climb: fix issue that crashed on real hardware

we were indexing off the end of the sprite and on real hardware the
uninitialied pointers there indexed into bad places

games/peasant_mini/cliff/hgr_sprite_bg_mask.s

@@ -52,6 +52,24 @@ hgr_draw_sprite_bg_mask:
 	sta	hdsb_ysize_smc+1
 	clc
 	adc	CURSOR_Y
+	cmp	#192
+	bcc	hdsb_ysize_ok
+
+hdsb_ysize_not_ok:
+	; adjust self modify
+        ; want it to be (192-SPRITE_Y)
+
+;        lda     #192
+ ;       sec
+  ;      sbc     SPRITE_Y
+   ;     sta     sprite_ysize_smc+1      ; self modify for end row
+
+        lda     #191                            ; max out yend
+
+
+
+hdsb_ysize_ok:
+
 	sta	save_yend,Y
 
 	;================================