I get "ValueError: images do not match"

```python
from staticmap import StaticMap, CircleMarker 
m = StaticMap(800, 600) 
marker = CircleMarker((7.21733093261719, 51.4838951030122), '#0036FF', 12)
m.add_marker(marker)
image = m.render(zoom=14)
```

python27
staticmap 0.5.4 
pillow 6.2.0