Update encrypt-and-decrypt-strings.cpp

Author: chenkkkabc

C++/encrypt-and-decrypt-strings.cpp

@@ -18,6 +18,7 @@ class Encrypter {
     string encrypt(string word1) {
         string result;
         for (const auto& c : word1) {
+            if (!lookup_.count(c)) return "";
             result += lookup_[c];
         }
         return result;