Handle key not exists errors for voltage sensor

Check the key exists or not before access sensor map.

Change-Id: I0ac5d63ae981ec2f984b1d464e93508560a4d030

rocm_smi/src/rocm_smi_monitor.cc

@@ -465,6 +465,8 @@ Monitor::getVoltSensorIndex(rsmi_voltage_type_t type) {
 
 rsmi_voltage_type_t
 Monitor::getVoltSensorEnum(uint64_t ind) {
+  // check if ind is a key or not
+  if (index_volt_type_map_.count(ind) == 0) return RSMI_VOLT_TYPE_INVALID;
   return index_volt_type_map_.at(ind);
 }