Groovy - Groovy ambiguous method overload

if (CollectionUtils.isEmpty(serviceGraph.getCallMap())) {
serviceGraph.setCallMap(newHashMap<String, Integer>())
}

Causedby: javax.script.ScriptException: groovy.lang.GroovyRuntimeException: Ambiguousmethodoverloadingformethodjava.math.BigDecimal#<init>.
Cannotresolvewhichmethodtoinvokefor [null] duetooverlappingprototypesbetween:
[class [Map]
[classjava.util.Collection]

if (CollectionUtils.isEmpty(serviceGraph.getCallMap() asMap)) {
serviceGraph.setCallMap(newHashMap<String, Integer>())
}