Fix crash caused by reading beyond the buffer. (#33449)

Author: yufengwangca

examples/chip-tool/commands/common/Command.cpp

@@ -171,7 +171,7 @@ bool HandleNullableOptional(Argument & arg, char * argValue, std::function<bool(
     if (arg.isNullable())
     {
         auto * nullable = reinterpret_cast<chip::app::DataModel::Nullable<T> *>(arg.value);
-        if (strcmp(argValue, "null") == 0)
+        if (argValue != nullptr && strncmp(argValue, "null", 4) == 0)
         {
             nullable->SetNull();
             return true;