scryptenc_print_error.c: add a "default" for safety

We should never reach that "default", but that doesn't mean that it'll
never happen.

Author: gperciva

lib/scryptenc/scryptenc_print_error.c

@@ -70,5 +70,8 @@ scryptenc_print_error(int rc, const char * infilename,
 	case SCRYPT_EPARAM:
 		warn0("Error in explicit parameters");
 		break;
+	default:
+		warn0("Programmer error: unrecognized scrypt error");
+		break;
 	}
 }