fix banjo duel crash

svn-id: r6427

scumm/gfx.cpp

@@ -851,6 +851,7 @@ byte Scumm::isMaskActiveAt(int l, int t, int r, int b, byte *mem)
 void Gdi::drawBitmap(byte *ptr, VirtScreen *vs, int x, int y, const int h,
 										 int stripnr, int numstrip, byte flag)
 {
+	assert(h > 0);
 	byte *backbuff_ptr, *bgbak_ptr, *smap_ptr;
 	int i;
 	byte *zplane_list[9];

scumm/object.cpp

@@ -356,7 +356,7 @@ void Scumm::drawObject(int obj, int arg)
 	ypos = od->y_pos;
 
 	width = od->width >> 3;
-	height = od->height &= 0xF8;	// Ender
+	height = od->height &= 0xFFFFFFF8;	// Mask out last 3 bits
 
 	if (width == 0 || xpos > _screenEndStrip || xpos + width < _screenStartStrip)
 		return;