core/src/main/java/io/fabric8/maven/core/util/MapUtil.java
public static void putAllIfNotNull(Map<String, String> ret, Map<String, String> toPut) {
        if (toPut != null) {
            ret.putAll(toPut);
        }
    }
public static void putAllIfNotNull(Map<String, String> ret, Map<String, String> toPut) {
        if (toPut != null) {
            ret.putAll(toPut);
        }
    }
Copies all of the elements i.e., the mappings, from toPut map into ret, if toPut isn't null.
@param ret
@param toPut