cipher.reset differs from MRI (raises error) when cipher.key is unset #5776

Environment

• Reproduced in:
  • jruby 9.2.8.0-SNAPSHOT (2.5.3) 2019-06-24 5bc9b15 OpenJDK 64-Bit Server VM 25.201-b09 on 1.8.0_201-b09 +jit [linux-x86_64]
  • jruby 9.1.14.0 (2.3.3) 2017-11-08 2176f24 OpenJDK 64-Bit Server VM 25.212-b03 on 1.8.0_212-b03 +jit [linux-x86_64]
• Linux 4.14.114-105.126.amzn2.x86_64 break script engine #1 SMP Tue May 7 02:26:40 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux

Expected Behavior

Tested in MRI Ruby 2.5 (ruby 2.5.5p157 (2019-03-15 revision 67260) [x86_64-linux])

require 'openssl'
cipher = OpenSSL::Cipher.new("AES-128-CBC")
cipher.reset
# success, no error is raised

Actual Behavior

require 'openssl'
cipher = OpenSSL::Cipher.new("AES-128-CBC")
cipher.reset
# raises error:
OpenSSL::Cipher::CipherError: key not specified
from org/jruby/ext/openssl/Cipher.java:944:in `reset'