rbus: fixup null pointer dereference in rbusEvent_SubscribeExRawData

[svc-rdkeportal01]

Fix NULL_RETURNS in rbusEvent_SubscribeExRawData

Issues Fixed

• Coverity CID 87: NULL_RETURNS in src/rbus/rbus.c at lines 5644 and 5655

Root Cause

rbusEventSubscription_find() can return NULL, but the returned pointer subInternal is dereferenced without NULL checks at:

• Line 5644: rbusMessage_AddPrivateListener(..., (void *)(subInternal->sub), subInternal->subscriptionId)
• Line 5655: rbusMessage_AddListener(..., (void *)(subInternal->sub), subInternal->subscriptionId)

This can cause a NULL pointer dereference if the subscription lookup fails.

Changes Made

Added NULL checks before dereferencing subInternal in two locations within the else block (after successful rbusEvent_SubscribeWithRetries):

Location 1 (myConn path):

if(!subInternal) {
    RBUSLOG_ERROR("%s: subInternal is NULL for event %s", __FUNCTION__, subscription[i].eventName);
    errorcode = RBUS_ERROR_INVALID_INPUT;
}
else {
    memset(rawDataTopic, '\0', strlen(rawDataTopic));
    snprintf(rawDataTopic, RBUS_MAX_NAME_LENGTH, "%s", subscription[i].eventName);
    errorcode = rbusMessage_AddPrivateListener(handle, rawDataTopic, _subscribe_rawdata_handler, 
                                                (void *)(subInternal->sub), subInternal->subscriptionId);
}

Location 2 (no myConn path):

if(!subInternal) {
    RBUSLOG_ERROR("%s: subInternal is NULL for event %s", __FUNCTION__, subscription[i].eventName);
    errorcode = RBUS_ERROR_INVALID_INPUT;
}
else {
    snprintf(rawDataTopic, RBUS_MAX_NAME_LENGTH, "rawdata.%s", subscription[i].eventName);
    errorcode = rbusMessage_AddListener(handle, rawDataTopic, _subscribe_rawdata_handler,
                                        (void *)(subInternal->sub), subInternal->subscriptionId);
}

Pattern Match

This fix follows the exact pattern from PR #370 (merged by Permanence AI) which fixed the same issue in rbusEvent_SubscribeRawData:

• NULL check with else block
• Error logging with function name and event name
• Set errorcode = RBUS_ERROR_INVALID_INPUT
• Continue processing (don't break loop)