Add more check to make sure code run safely.

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@10574 6f19259b-4bc3-4df7-8a09-765794883524

EdkCompatibilityPkg/Foundation/Library/Dxe/EfiDriverLib/Perf.c

@@ -1,6 +1,6 @@
 /*++
 
-Copyright (c) 2004 - 2005, Intel Corporation. All rights reserved.<BR>
+Copyright (c) 2004 - 2010, Intel Corporation. All rights reserved.<BR>
 This program and the accompanying materials                          
 are licensed and made available under the terms and conditions of the BSD License         
 which accompanies this distribution.  The full text of the license may be found at        
@@ -825,6 +825,11 @@ Returns:
     return EFI_OUT_OF_RESOURCES;
   }
 
+  //
+  // Initialize 'LogHob' to NULL before usage.
+  //
+  LogHob = NULL;
+
   if (Ticker != 0) {
     TimerValue = Ticker;
   } else {
@@ -837,7 +842,10 @@ Returns:
   EfiLibGetSystemConfigurationTable (&gEfiHobListGuid, &HobList);
   do {
     Status = GetNextGuidHob (&HobList, &gEfiPeiPerformanceHobGuid, (VOID **) &LogHob, NULL);
-    if (EFI_ERROR (Status)) {
+    if (EFI_ERROR (Status) || (LogHob == NULL)) {
+      //
+      // Failed to get HOB for ProtocolGuid.
+      //
       break;
     }