Inspect mLoggerInfo before accessing in the event callback (#345)

## Description

This change adds an inspection of `mLoggerInfo` variable before reading
from GetTime() runtime service. As the advanced logger design expects
the `mLoggerInfo` to be set to NULL, we should always check the pointer
before usage, otherwise page fault could occur under certain edge cases.

- [x] Impacts functionality?
- **Functionality** - Does the change ultimately impact how firmware
functions?
- Examples: Add a new library, publish a new PPI, update an algorithm,
...
- [ ] Impacts security?
- **Security** - Does the change have a direct security impact on an
application,
    flow, or firmware?
  - Examples: Crypto algorithm change, buffer overflow fix, parameter
    validation improvement, ...
- [ ] Breaking change?
- **Breaking change** - Will anyone consuming this change experience a
break
    in build or boot behavior?
- Examples: Add a new library class, move a module to a different repo,
call
    a function in a new library class in a pre-existing module, ...
- [ ] Includes tests?
  - **Tests** - Does the change include any explicit test code?
  - Examples: Unit tests, integration tests, robot tests, ...
- [ ] Includes documentation?
- **Documentation** - Does the change contain explicit documentation
additions
    outside direct code modifications (and comments)?
- Examples: Update readme file, add feature readme file, link to
documentation
    on an a separate Web page, ...

## How This Was Tested

This was tested on QEMU Q35 platform.

## Integration Instructions

N/A

---------

Co-authored-by: Michael Kubacki <[email protected]>

AdvLoggerPkg/Library/AdvancedLoggerLib/DxeCore/AdvancedLoggerLib.c

@@ -189,11 +189,13 @@ OnRealTimeClockArchNotification (
 
   SystemTable->BootServices->CloseEvent (Event);
 
-  Status = SystemTable->RuntimeServices->GetTime ((EFI_TIME *)&mLoggerInfo->Time, NULL);
-  if (EFI_ERROR (Status)) {
-    DEBUG ((DEBUG_INFO, "%a: error getting real time. Code=%r\n", __FUNCTION__, Status));
-  } else {
-    mLoggerInfo->TicksAtTime = GetPerformanceCounter ();
+  if (mLoggerInfo != NULL) {
+    Status = SystemTable->RuntimeServices->GetTime ((EFI_TIME *)&mLoggerInfo->Time, NULL);
+    if (EFI_ERROR (Status)) {
+      DEBUG ((DEBUG_ERROR, "%a: error getting real time. Code=%r\n", __func__, Status));
+    } else {
+      mLoggerInfo->TicksAtTime = GetPerformanceCounter ();
+    }
   }
 
   return;