If I declare a `MutableMap<String,String>` a...

# getting-started

[v79]

If I declare a MutableMap<String,String> and check that the map contains a given key, why does getting the value return a nullable type? There's no null allowed in MutableMap<String,String>, surely? e.g.

val propNameCache: MutableMap<String,String> = mutableMapOf()
		val cacheKey: String = "$propertyKey:$lang"
		if(propNameCache.containsKey(cacheKey)) {
			return propNameCache[cacheKey]
		}