java.nio.charset.MalformedInputException: Input length = 1 by import groovy script

**DanP** ([Bug 65039](https://bz.apache.org/bugzilla//show_bug.cgi?id=65039&redirect=false)):
When I import a groovy script with umlauts in comments and strings, I get the following error message. In version 5.3 everything was still OK.

for example:
// work in progress --> statusDe":"Beschäftigt","akt":34,"status":20 ...

error message

2020-12-29 11:20:23,500 ERROR o.a.j.e.JSR223PostProcessor: Problem in JSR223 script, ExtractRepeatQuery
javax.script.ScriptException: java.nio.charset.MalformedInputException: Input length = 1
at org.codehaus.groovy.jsr223.GroovyScriptEngineImpl.readFully(GroovyScriptEngineImpl.java:458) ~[groovy-jsr223-3.0.5.jar:3.0.5]
at org.codehaus.groovy.jsr223.GroovyScriptEngineImpl.compile(GroovyScriptEngineImpl.java:188) ~[groovy-jsr223-3.0.5.jar:3.0.5]
at org.apache.jmeter.util.JSR223TestElement.processFileOrScript(JSR223TestElement.java:186) ~[ApacheJMeter_core.jar:5.4]
at org.apache.jmeter.extractor.JSR223PostProcessor.process(JSR223PostProcessor.java:45) [ApacheJMeter_components.jar:5.4]
at org.apache.jmeter.threads.JMeterThread.runPostProcessors(JMeterThread.java:952) [ApacheJMeter_core.jar:?]
at org.apache.jmeter.threads.JMeterThread.executeSamplePackage(JMeterThread.java:573) [ApacheJMeter_core.jar:?]
at org.apache.jmeter.threads.JMeterThread.processSampler(JMeterThread.java:489) [ApacheJMeter_core.jar:?]
at org.apache.jmeter.threads.JMeterThread.run(JMeterThread.java:256) [ApacheJMeter_core.jar:?]
at java.lang.Thread.run(Thread.java:832) [?:?]
Caused by: java.nio.charset.MalformedInputException: Input length = 1
at java.nio.charset.CoderResult.throwException(CoderResult.java:274) ~[?:?]
at sun.nio.cs.StreamDecoder.implRead(StreamDecoder.java:352) ~[?:?]
at sun.nio.cs.StreamDecoder.read(StreamDecoder.java:188) ~[?:?]
at java.io.InputStreamReader.read(InputStreamReader.java:181) ~[?:?]
at java.io.BufferedReader.read1(BufferedReader.java:210) ~[?:?]
at java.io.BufferedReader.read(BufferedReader.java:287) ~[?:?]
at org.codehaus.groovy.jsr223.GroovyScriptEngineImpl.readFully(GroovyScriptEngineImpl.java:454) ~[groovy-jsr223-3.0.5.jar:3.0.5]
... 8 more

Severity: normal
OS: All