rbus: fix NULL pointer dereference in rbusEvent_SubscribeRawData

[svc-rdkeportal01]

Issue Fixed

Coverity Defect: FORWARD_NULL
CWE: CWE-476 (NULL Pointer Dereference)
Severity: HIGH
Function: rbusEvent_SubscribeRawData
File: src/rbus/rbus.c

Root Cause

The function rbusEvent_SubscribeRawData calls rbusEventSubscription_find() which can return NULL, but then unconditionally dereferences the returned pointer when accessing subInternal->sub and subInternal->subscriptionId.

This occurs in two locations:

1. Line 5322 - In the if(myConn) branch when calling rbusMessage_AddPrivateListener()
2. Line 5340 - In the else branch when calling rbusMessage_AddListener()

Changes Made

Added NULL checks before dereferencing subInternal in both branches:

Location 1: if(myConn) branch

if(subInternal)
{
    errorcode = rbusMessage_AddPrivateListener(handle, rawDataTopic, _subscribe_rawdata_handler, 
                                                (void *)(subInternal->sub), subInternal->subscriptionId);
}
else
{
    RBUSLOG_ERROR("%s: subInternal is NULL for %s", __FUNCTION__, eventName);
    errorcode = RBUS_ERROR_INVALID_INPUT;
}

Location 2: else branch

if(subInternal)
{
    errorcode = rbusMessage_AddListener(handle, rawDataTopic,
                                        _subscribe_rawdata_handler, (void *)(subInternal->sub), 
                                        subInternal->subscriptionId);
}
else
{
    RBUSLOG_ERROR("%s: subInternal is NULL for %s", __FUNCTION__, eventName);
    errorcode = RBUS_ERROR_INVALID_INPUT;
}

Why This Fix is Correct

1. Prevents crash - NULL pointer dereference would cause segmentation fault
2. Proper error handling - Returns RBUS_ERROR_INVALID_INPUT when subscription not found
3. Consistent with codebase - Other call sites already check for NULL
4. Maintains functionality - Only adds safety check, doesn't change logic
5. Clear error logging - Logs which event name caused the NULL condition

Testing

• Verified fix compiles without errors
• Checked that error path is properly handled
• Confirmed both branches (if and else) are fixed