No output with minify using ADVANCED_MODE

[DrifterAtSea]

I ran the minify task but no output was created. I created an "externs" file for jquery 3.1.1 using the online tool at:

http://www.dotnetwise.com/Code/Externs/

The minify task runs without any errors but the output file that it creates has nothing in it. Here is my gradle.build file:

plugins {
    id "com.eriwen.gradle.js" version "2.14.1"
}

javascript.source {
    dev {
        js {
            srcDir 'scripts'
            include "*.js"
            exclude "*.min.js"
        }
    }
    prod {
        js {
            srcDir 'scripts'
            include "*.min.js"
        }
    }
}

// Configure the built-in task
combineJs {
    encoding = "UTF-8"
    source = javascript.source.dev.js.files
    dest = file("${buildDir}/shodogg-mid-1.0.0.js")
}

minifyJs {
    source = combineJs
    dest = file("${buildDir}/shodogg-mid-1.0.0-min.js")
    sourceMap = file("${buildDir}/all.sourcemap.json")
    closure {
        warningLevel = 'VERBOSE'
        compilerOptions.languageIn = "ECMASCRIPT5"
        compilationLevel = "ADVANCED_OPTIMIZATIONS"
        externs = files("scripts/externs/jquery-3.1.1-externs.js")
    }
}