[utils] check whether mInfo.mTxInfo.mIeInfo is null before using it (openthread#11238)

The simulation platform radio driver doesn't set the 'mInfo.mTxInfo.mIeInfo'
field of the ACK frame. And the function 'otMacFrameUpdateTimeIe()' directly
use the 'mInfo.mTxInfo.mIeInfo' field, this may cause the program crash.

This commit checks whether 'mInfo.mTxInfo.mIeInfo' is null before using it
and sets the 'mInfo.mTxInfo.mIeInfo' field of the ACK frame to null in
simulation platform.

Author: zhanglongxia

Diff for: examples/platforms/simulation/radio.c

@@ -420,6 +420,7 @@ void platformRadioInit(void)
 #else
     sTransmitFrame.mInfo.mTxInfo.mIeInfo = NULL;
 #endif
+    sAckFrame.mInfo.mTxInfo.mIeInfo = NULL;
 
     for (size_t i = 0; i <= kMaxChannel - kMinChannel; i++)
     {

Diff for: examples/platforms/utils/mac_frame.cpp

@@ -380,20 +380,24 @@ otError otMacFrameProcessTransmitSecurity(otRadioFrame *aFrame, otRadioContext *
 #if OPENTHREAD_CONFIG_TIME_SYNC_ENABLE
 void otMacFrameUpdateTimeIe(otRadioFrame *aFrame, uint64_t aRadioTime, otRadioContext *aRadioContext)
 {
-    if (aFrame->mInfo.mTxInfo.mIeInfo->mTimeIeOffset != 0)
-    {
-        uint8_t *timeIe = aFrame->mPsdu + aFrame->mInfo.mTxInfo.mIeInfo->mTimeIeOffset;
-        uint64_t time   = aRadioTime + aFrame->mInfo.mTxInfo.mIeInfo->mNetworkTimeOffset;
+    uint8_t *timeIe;
+    uint64_t time;
+
+    VerifyOrExit((aFrame->mInfo.mTxInfo.mIeInfo != nullptr) && (aFrame->mInfo.mTxInfo.mIeInfo->mTimeIeOffset != 0));
 
-        *timeIe = aFrame->mInfo.mTxInfo.mIeInfo->mTimeSyncSeq;
+    timeIe  = aFrame->mPsdu + aFrame->mInfo.mTxInfo.mIeInfo->mTimeIeOffset;
+    time    = aRadioTime + aFrame->mInfo.mTxInfo.mIeInfo->mNetworkTimeOffset;
+    *timeIe = aFrame->mInfo.mTxInfo.mIeInfo->mTimeSyncSeq;
 
+    *(++timeIe) = static_cast<uint8_t>(time & 0xff);
+    for (uint8_t i = 1; i < sizeof(uint64_t); i++)
+    {
+        time        = time >> 8;
         *(++timeIe) = static_cast<uint8_t>(time & 0xff);
-        for (uint8_t i = 1; i < sizeof(uint64_t); i++)
-        {
-            time        = time >> 8;
-            *(++timeIe) = static_cast<uint8_t>(time & 0xff);
-        }
     }
+
+exit:
+    return;
 }
 #endif // OPENTHREAD_CONFIG_TIME_SYNC_ENABLE