Merge pull request #11187 from duncanspumpkin/fix_11174

Fix format string

src/openrct2/localisation/Localisation.cpp

@@ -370,7 +370,9 @@ static void format_append_string(char** dest, size_t* size, const utf8* string)
 {
     if ((*size) == 0)
         return;
-    size_t length = strlen(string);
+    if (string == nullptr)
+        return;
+    size_t length = strnlen(string, *size);
     if (length < (*size))
     {
         std::memcpy((*dest), string, length);