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/UefiShellLevel1CommandsLib/If.c

@@ -739,6 +739,9 @@ MoveToTagSpecial (
     //
     CommandName   = NULL;
     CommandName   = StrnCatGrow(&CommandName, NULL, CommandNode->Cl, 0);
+    if (CommandName == NULL) {
+      continue;
+    }
     CommandWalker = CommandName;
     while (CommandWalker[0] == L' ') {
       CommandWalker++;