rbus: fixup null returns in getEventTableInstNum

[svc-rdkeportal01]

Fix NULL_RETURNS in getEventTableInstNum

Issues Fixed

• Coverity CID 85: NULL_RETURNS in test/rbus/provider/rbusTestProvider.c at line 1337

Root Cause

strstr() can return NULL if the substring "EventsTable." is not found in the input string. The original code adds 12 to the result without checking for NULL, then immediately dereferences it, which can cause a segmentation fault.

Changes Made

Added NULL check before using the pointer returned by strstr():

Before:

char const* pinstNum = strstr(propName, "EventsTable.") + 12;
buff[0] = *pinstNum;  // Crash if strstr returned NULL

After:

char const* pinstNum = strstr(propName, "EventsTable.");

if(!pinstNum) {
    printf("%s: EventsTable not found in %s\n", __FUNCTION__, propName);
    return 0;  // Return default value
}

pinstNum += 12;  // Move past "EventsTable."
buff[0] = *pinstNum;  // Safe to dereference now

• Line: 1337