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/UefiShellLevel3CommandsLib/Touch.c

@@ -79,11 +79,16 @@ DoTouchByHandle (
 
   if (FS == NULL) {
     FS = StrnCatGrow(&FS, NULL, Name, 0);
-    TempSpot = StrStr(FS, L"\\");
-    if (TempSpot != NULL) {
-      *TempSpot = CHAR_NULL;
+    if (FS != NULL) {
+      TempSpot = StrStr(FS, L"\\");
+      if (TempSpot != NULL) {
+        *TempSpot = CHAR_NULL;
+      }
     }
   }
+  if (FS == NULL) {
+    return (EFI_INVALID_PARAMETER);
+  }
 
   //
   // do it