If IDL structure contains string and char fields, and generated *Helper#write method looks like
ostream.write_string (value.string_field); //empty string
ostream.write_char (value.char_field); //any char
without non-empty strings before char field, then write_char method will fail with stacktrace:
Caused by: java.lang.ArrayIndexOutOfBoundsException: 0
at com.sun.corba.se.impl.encoding.CodeSetConversion$JavaCTBConverter.convert(CodeSetConversion.java:206) [openjdk-orb-8.0.6.Final.jar:8.0.6.Final]
at com.sun.corba.se.impl.encoding.CDROutputStream_1_0.write_char(CDROutputStream_1_0.java:318) [openjdk-orb-8.0.6.Final.jar:8.0.6.Final]
at com.sun.corba.se.impl.encoding.CDROutputStream.write_char(CDROutputStream.java:138) [openjdk-orb-8.0.6.Final.jar:8.0.6.Final]
at SomeClassHelper.write(SomeClassHelper.java:<some line>)

Suggested fix is in attachment "empty_string_followed_by_char_conversion_suggested_fix.patch"