RAS: ras_common: Add null pointer check for error record probe function

Add a null pointer check for the error record probe
function -- avoids a panic in case a platform has not defined it.

Change-Id: I1139fa0df33297a12ec16615cacd07540925f991
Signed-off-by: Sughosh Ganu <sughosh.ganu@arm.com>

lib/extensions/ras/ras_common.c

@@ -114,9 +114,10 @@ static int ras_interrupt_handler(uint32_t intr_raw, uint32_t flags,
 		panic();
 	}
 
-
-	ret = selected->err_record->probe(selected->err_record, &probe_data);
-	assert(ret != 0);
+	if (selected->err_record->probe) {
+		ret = selected->err_record->probe(selected->err_record, &probe_data);
+		assert(ret != 0);
+	}
 
 	/* Call error handler for the record group */
 	assert(selected->err_record->handler != NULL);