use a number for the maximum indentation instead of relying on str::len()

src/bin/miri.rs

@@ -44,8 +44,8 @@ fn init_logger() {
     let format = |record: &log::LogRecord| {
         // prepend spaces to indent the final string
         let indentation = log_settings::settings().indentation;
-        let spaces = "    |    |    |    |    |    |    |    |    ";
-        let indentation = &spaces[..std::cmp::min(indentation, spaces.len())];
+        let spaces = "    |    |    |    |    |    |    |    |    |";
+        let indentation = &spaces[..std::cmp::min(indentation, 44)];
         format!("{}:{}|{} {}", record.level(), record.location().module_path(), indentation, record.args())
     };