MdeModulePkg AtaAtapiPassThru: Skip the potential NULL pointer access

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3732
Recent change c9742578 exposes this potential issue.

Signed-off-by: Liming Gao <gaoliming@byosoft.com.cn>
Acked-by: Rebecca Cran <rebecca@nuviainc.com>
Reviewed-by: Hao A Wu <hao.a.wu@intel.com>

MdeModulePkg/Bus/Ata/AtaAtapiPassThru/AhciMode.c

@@ -885,6 +885,13 @@ AhciPrintStatusBlock (
   IN UINT32                DebugLevel
   )
 {
+  //
+  // Skip NULL pointer
+  //
+  if (AtaStatusBlock == NULL) {
+    return;
+  }
+
   //
   // Only print status and error since we have all of the rest printed as
   // a part of command block print.