res_speech_aeap: add aeap error handling

res_speech_aeap previously did not register an error handler
with aeap, so it was not notified of a disconnect. This resulted
in SpeechBackground never exiting upon a websocket disconnect.

Resolves: #303
(cherry picked from commit 792ad9fec8)

res/res_speech_aeap.c

@@ -350,11 +350,29 @@ static const struct ast_aeap_message_handler request_handlers[] = {
 	{ "set", handle_request_set },
 };
 
+/*!
+ * \internal
+ * \brief Handle an error from an external application by setting state to done
+ *
+ * \param aeap Pointer to an Asterisk external application object
+ */
+static void ast_aeap_speech_on_error(struct ast_aeap *aeap)
+{
+	struct ast_speech *speech = ast_aeap_user_data_object_by_id(aeap, "speech");
+	if (!speech) {
+		ast_log(LOG_ERROR, "aeap generated error with no associated speech object");
+		return;
+	}
+
+	ast_speech_change_state(speech, AST_SPEECH_STATE_DONE);
+}
+
 static struct ast_aeap_params speech_aeap_params = {
 	.response_handlers = response_handlers,
 	.response_handlers_size = ARRAY_LEN(response_handlers),
 	.request_handlers = request_handlers,
 	.request_handlers_size = ARRAY_LEN(request_handlers),
+	.on_error = ast_aeap_speech_on_error,
 };
 
 /*!