ati-vga: Do not assert on error

Do not abort on unsupported value just print log and continue. While
display will likely be broken this prevents malicious guest to crash
QEMU causing denial of service.

Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
Message-id: 0c13dab5d8e3b7e7479c3edbf53aeac8c09de6de.1592737958.git.balaton@eik.bme.hu
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

hw/display/ati.c

@@ -86,8 +86,8 @@ static void ati_vga_switch_mode(ATIVGAState *s)
                 break;
             default:
                 qemu_log_mask(LOG_UNIMP, "Unsupported bpp value\n");
+                return;
             }
-            assert(bpp != 0);
             DPRINTF("Switching to %dx%d %d %d @ %x\n", h, v, stride, bpp, offs);
             vbe_ioport_write_index(&s->vga, 0, VBE_DISPI_INDEX_ENABLE);
             vbe_ioport_write_data(&s->vga, 0, VBE_DISPI_DISABLED);