panic if comments are too long

No one is going to put >99999 characters in the comment field realistically and the UI is likely to freeze and crash before the application gets to this point. So a raw panic is sufficient for this extreme edge case.

src/Picocrypt.go

@@ -18,6 +18,7 @@ import (
 	"crypto/hmac"
 	"crypto/rand"
 	"crypto/subtle"
+	"errors"
 	"flag"
 	"fmt"
 	"hash"
@@ -1316,6 +1317,10 @@ func work() {
 		// Write the program version to file
 		_, errs[0] = fout.Write(rsEncode(rs5, []byte(version)))
 
+		if len(comments) > 99999 {
+			panic(errors.New("comments exceed maximum length"))
+		}
+
 		// Encode and write the comment length to file
 		commentsLength := []byte(fmt.Sprintf("%05d", len(comments)))
 		_, errs[1] = fout.Write(rsEncode(rs5, commentsLength))