From OJI sources, a call is made to proxyEnv->Get<PrimitiveType>ArrayElements(...)
(modules/oji/src/ProxyJNI.cpp file of Mozilla tree)

  #define IMPLEMENT_GET_ARRAY_ELEMENTS(methodName, type) static type* JNICALL methodName(JNIEnv *env, type##Array array, jboolean *isCopy) { type* outElements = NULL; \ <- note that here it's set to NULL
        ^^^^^^^^^^^^^^^^^^^^^^^^
        nsISecureEnv* secureEnv = GetSecureEnv(env); nsresult result; result = secureEnv->GetArrayElements(type##_type, array, isCopy, &outElements); \ <- see the code below: outElements never
changes
                                                                         ^^^^^^^^^^^^
        return outElements; <- here we always return NULL to user
    }
  IMPLEMENT_GET_ARRAY_ELEMENTS(GetBooleanArrayElements, jboolean)
  IMPLEMENT_GET_ARRAY_ELEMENTS(GetByteArrayElements, jbyte)
  ....



The implementation of secureEnv->GetArrayElements(...)
method is the following (src/motif/navug5/CSecureJNIEnv.cpp file in OJI Plugin tree):
  
NS_IMETHODIMP CSecureJNIEnv::GetArrayElements(/*[in]*/ jni_type element_type,
                                            /*[in]*/ jarray array,
                                            /*[in]*/ jboolean *isCopy,
                                            /*[out]*/ void* result) <- &outElements comes here as void* though better to make it
void** but it doesn't really matter
                                            ^^^^^^^^^^^^^^^^^^^^^^^
{
  fprintf(stderr, "CSecureJNI::GetArrayElements is called !\n");
    if (m_env == NULL || result == NULL)
        return NS_ERROR_NULL_POINTER;

    fprintf(stderr, "CSecureJNI::GetArrayElements: switch by type ...\n");
    switch (element_type)
    {
        case jboolean_type: {
            result = (void*) m_env->GetBooleanArrayElements((jbooleanArray)array, isCopy); <- but in this line we actually affect
local "result" variable only and doesn't affect outElements anyhow
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
            break;
        }
    ...
}

The most simple way to fix this bug is to make the following change in the code:
            *(void**)result = (void*) m_env->GetBooleanArrayElements((jbooleanArray)array, isCopy);
I tried it out - it works OK.