parser_json: Add EncodingError to rescue list for oj 3.x. fix #1866

[repeatedly]

oj 3.x sometimes raises an EncodingError for input string and it beaks parser_json behaviour.
This patch fixes it.

Here is test code:

Oj.load('+ cat /etc/resolv.conf')

• oj 3.4.0

test_oj.rb:6:in `load': Empty input at line 1, column 1 [parse.c:926] in '+ cat /etc/resolv.conf (EncodingError)

• oj 2.18.5

test_oj.rb:6:in `load': unexpected character at line 1, column 3 [parse.c:671] (Oj::ParseError)