ShellPkg: Add checking for memory allocation and pointer returns from functions.

signed-off-by: jcarsey
reviewed-by: geekboy15a

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@12540 6f19259b-4bc3-4df7-8a09-765794883524

ShellPkg/Library/UefiShellLevel2CommandsLib/Map.c

@@ -414,6 +414,9 @@ PerformSingleMappingDisplay(
 
   CurrentName = NULL;
   CurrentName = StrnCatGrow(&CurrentName, 0, MapList, 0);
+  if (CurrentName == NULL) {
+    return (EFI_OUT_OF_RESOURCES);
+  }
   TempSpot = StrStr(CurrentName, L";");
   if (TempSpot != NULL) {
     *TempSpot = CHAR_NULL;