Ruby: 3.7 segfaults on BytesValue#to_json

[fables-tales]

What version of protobuf and what language are you using?
Version: v3.7.0 & Master
Language: Ruby

What operating system (Linux, Windows, ...) and version?
OS X 10.14.3

What runtime / compiler are you using (e.g., python version or gcc version)
ruby 2.5.3p105 (2018-10-18 revision 65156) [x86_64-darwin18]

What did you do?
Steps to reproduce the behavior:

curl http://2.gravatar.com/avatar/8ca3202a7c4591caa91e66cf4ad4b116?s=1000 > sam.jpg
ruby -e 'require "google/protobuf"; require "google/protobuf/wrappers_pb"; Google::Protobuf::BytesValue.new(value: File.open("sam.jpg", "rb").read).to_json'

What did you expect to see
Not a segfault, but instead some JSON output for this value.

What did you see instead?
The ruby virtual machine segfaults

/Users/samphippen/.gem/ruby/2.5.3/gems/google-protobuf-3.7.0-universal-darwin/lib/google/protobuf/message_exts.rb:44: [BUG] Segmentation fault at 0x00007ffee028c000
ruby 2.5.3p105 (2018-10-18 revision 65156) [x86_64-darwin18]

-- Crash Report log information --------------------------------------------
   See Crash Report log file under the one of following:
     * ~/Library/Logs/DiagnosticReports
     * /Library/Logs/DiagnosticReports
   for more details.
Don't forget to include the above Crash Report log file in bug reports.

-- Control frame information -----------------------------------------------
c:0004 p:---- s:0017 e:000016 CFUNC  :encode_json
c:0003 p:0014 s:0011 e:000010 METHOD /Users/samphippen/.gem/ruby/2.5.3/gems/google-protobuf-3.7.0-universal-darwin/lib/google/protobuf/message_exts.rb:44
c:0002 p:0048 s:0006 e:000005 EVAL   -e:1 [FINISH]
c:0001 p:0000 s:0003 E:001170 (none) [FINISH]

-- Ruby level backtrace information ----------------------------------------
-e:1:in `<main>'
/Users/samphippen/.gem/ruby/2.5.3/gems/google-protobuf-3.7.0-universal-darwin/lib/google/protobuf/message_exts.rb:44:in `to_json'
/Users/samphippen/.gem/ruby/2.5.3/gems/google-protobuf-3.7.0-universal-darwin/lib/google/protobuf/message_exts.rb:44:in `encode_json'

-- Machine register context ------------------------------------------------
 rax: 0x0000000000000043 rbx: 0x0000000000000037 rcx: 0x000000000000004e
 rdx: 0x000000010ff04dc4 rdi: 0x0000000000034b37 rsi: 0x000000010fec8c40
 rbp: 0x00007ffee0289700 rsp: 0x00007ffee0285850  r8: 0x0000000000000000
  r9: 0x0000000000000001 r10: 0x0000000000000002 r11: 0x0000000000000002
 r12: 0x00007ffee028c000 r13: 0x00007fd36a7a9440 r14: 0x00000000000398fb
 r15: 0x00007ffee0289a30 rip: 0x000000010feb3def rfl: 0x0000000000010203

-- C level backtrace information -------------------------------------------

(c level backtrace information is not populated)

Anything else we should know about your project / environment

This was first reproduced while building examples for the google ads ruby client library, where our MediaImage proto uses a bytesvalue to wrap an image to upload, the provided image is a test image we were using to reproduce the behavior. My LDAP is samphippen@ if you need to reach out for any google confidential stuff :)