Small fixes

src/include/tokenize.h

@@ -13,7 +13,7 @@ using TokenData = variant<int, string, Type>;
 
 struct Token {
     TokenType type;
-    TokenData data;
+    TokenData data { };
 };
 
 /*

src/tokenize.cpp

@@ -128,11 +128,11 @@ vector<Token> tokenize(string str) {
             tokens.emplace_back(token);
             str.erase(0, 1);
         }
-        else if (isspace(str[0])) {
+        else if (isspace(str[0]) || str[0] == '\0') {
             str.erase(0, 1);
         }
         else {
-            cerr << "Unknown token: " << str << endl;
+            cerr << "Unknown token: \"" << str << "\"" << endl;
             break;
         }
     }