Updated: Log & Panic if called before door.Init().

Before door.Init is called, we don't know if we need
CP437 or Unicode.

ansi-to-go/ansi-to-go.go

@@ -71,6 +71,9 @@ func readfile(filename string) {
 		fmt.Printf("    \"%s\",\n", repr_line(line))
 	}
 	fmt.Println("  }")
+	fmt.Println("  if !door.Unicode && !door.CP437 {")
+	fmt.Println("    log.Panicf(\"Call after door.Init() so Unicode/CP437 has been set.\")")
+	fmt.Println("  }")
 	fmt.Println("  if door.Unicode {")
 	fmt.Println("    for idx := range data {")
 	fmt.Println("      data[idx] = door.CP437_to_Unicode(data[idx])")
@@ -94,7 +97,7 @@ func main() {
 	}
 
 	fmt.Printf("package %s\n\n", defaultPackage)
-	fmt.Printf("import (\n  \"red-green/door\"\n  )\n\n")
+	fmt.Printf("import (\n  \"red-green/door\"\n  \"log\"\n  )\n\n")
 	for _, filename := range flag.Args() {
 		readfile(filename)
 	}