source=="osm" requires google key if bbox not specified

code that requires google even for `source=="osm"`
```
if (source == "osm") {
if (location_type != "bbox") {
gm <- get_googlemap(center = location, zoom = zoom,
filename = filename)
location <- as.numeric(attr(gm, "bb"))[c(2, 1, 4,
3)]
}
return(get_openstreetmap(bbox = location, scale = scale,
messaging = messaging, urlonly = urlonly, filename = filename,
color = color))
}

```