A DESCRIPTION OF THE PROBLEM :
#Version: jdk-12.0.1, jdk-11.0.3

#Testcase:
1. var NISLFuzzingFunc = function (target_test, target) {
2. print(target_test[0][0]) //undefined
3. target_test = target_test[0];
4. print(target_test[0]); //NaN
5. print("==================================");
6. print(target[0][0]); //undefined
7. target = target[0];
8. print(target[0]); //undefined
9. };
10. var NISLParameter0 = [62303, 0.8726223721680498];
11. var NISLParameter1 = [62303];
12. NISLFuzzingFunc(NISLParameter0, NISLParameter1);

#Command:
./nashorn/jdk-12.0.1/bin/jjs --no-syntax-extensions=true --no-deprecation-warning=true testcase.js

#Output:
undefined
NaN
==================================
undefined
undefined

#Expected output:
undefined
undefined
==================================
undefined
undefined

#Description:
    For the above testcase, the output of Line 4 should be consistent with the output of Line 2, and should be "undefined", but the output of Line 4 is "NaN". We try to delve into the reasons, if the elements of the array do not contain a decimal(such as NISLParameter1), the output of Line 8 is the normal value "undefined". When there is a decimal in the array (NISLParameter0), the output of the 4th Line will be abnormal.
   Is this a bug of Nashorn? Looking forward to your reply.