Getting error if supplied empty customTypesMapping array

[Bogdan Kobylynskyi]

Sample config:

graphqlCodegen {
    graphqlSchemaPaths = [
            "$projectDir/src/main/resources/workflow.graphqls".toString()
    ]
    outputDir = new File("$buildDir/generated".toString())
    packageName = "com.xxx.workflow.graphql"
    customTypesMapping = [ ]
    modelNameSuffix = "TO"
}

Error while generation:

Cannot cast object '[]' with class 'java.util.ArrayList' to class 'java.util.Map' due to: groovy.lang.GroovyRuntimeException: Could not find matching constructor for: java.util.Map()