Why is compiling my Closure code with Plovr giving me weird symbols?

Question

I ran java -jar ~/PlovrFiles/plovr.jar build ~/js/config.js > /tmp/compiled.js

However, the Closure compiler issues a bizarre error with weird symbols such as RPP?LQ?RP*)?K??,)I?S??$?d?$?.

Exception in thread "main" com.google.gson.JsonSyntaxException: com.google.gson.stream.MalformedJsonException: Expected literal value near ??*??RPP?LQ?RP*)?K??,)I?S??$?d?$? ???
    at com.google.gson.JsonParser.parse(JsonParser.java:64)
    at com.google.gson.JsonParser.parse(JsonParser.java:44)
    at org.plovr.ConfigParser.createBuilderFromFile(ConfigParser.java:29)
    at org.plovr.ConfigParser.parseFile(ConfigParser.java:98)
    at org.plovr.cli.BuildCommand.runCommandWithOptions(BuildCommand.java:55)
    at org.plovr.cli.BuildCommand.runCommandWithOptions(BuildCommand.java:31)
    at org.plovr.cli.AbstractCommandRunner.runCommand(AbstractCommandRunner.java:41)
    at org.plovr.cli.Command.execute(Command.java:47)
    at org.plovr.cli.Main.mainWithExitCode(Main.java:56)
    at org.plovr.cli.Main.main(Main.java:30)
Caused by: com.google.gson.stream.MalformedJsonException: Expected literal value near ??*??RPP?LQ?RP*)?K??,)I?S??$?d?$? ???
    at com.google.gson.stream.JsonReader.syntaxError(JsonReader.java:1111)
    at com.google.gson.stream.JsonReader.readLiteral(JsonReader.java:1079)
    at com.google.gson.stream.JsonReader.nextValue(JsonReader.java:808)
    at com.google.gson.stream.JsonReader.quickPeek(JsonReader.java:382)
    at com.google.gson.stream.JsonReader.peek(JsonReader.java:340)
    at com.google.gson.JsonParser.parse(JsonParser.java:59)
    ... 9 more
t.js

At first, I thought these symbols were due to the hidden cache files produced by my text editor JEdit. However, deleting those files did not do away with this error. None of the files in my path seem to have these symbols. Any advice on where I could look to debug this error?

Here is my simple config.js file.

// File: config.js
{
  "id": "myApp",
  "paths": ".",
  "inputs": "mainengine.js"
}