Remove extra vertical space for any label with no message set (#82)

* remove empty lines for any label with no message in report

* change labels messages in new simple example

examples/simple.rs

@@ -1,4 +1,5 @@
-use ariadne::{Report, ReportKind, Label, Source};
+use yansi::Color;
+use ariadne::{Report, ReportKind, Label, Source, Config};
 
 fn main() {
     Report::build(ReportKind::Error, (), 34)
@@ -8,4 +9,17 @@ fn main() {
         .finish()
         .print(Source::from(include_str!("sample.tao")))
         .unwrap();
+
+    const SOURCE: &str = "a b c d e f";
+    // also supports labels with no messages to only emphasis on some areas
+    Report::build(ReportKind::Error, (), 34)
+        .with_message("Incompatible types")
+        .with_config(Config::default().with_compact(true))
+        .with_label(Label::new(0..1).with_color(Color::Red))
+        .with_label(Label::new(2..3).with_color(Color::Blue).with_message("`b` for banana").with_order(1))
+        .with_label(Label::new(4..5).with_color(Color::Green))
+        .with_label(Label::new(7..9).with_color(Color::Cyan).with_message("`e` for emerald"))
+        .finish()
+        .print(Source::from(SOURCE))
+        .unwrap();
 }

src/write.rs

@@ -608,7 +608,10 @@ impl<S: Span> Report<'_, S> {
                 // Arrows
                 for row in 0..line_labels.len() {
                     let line_label = &line_labels[row];
-
+                    //No message to draw thus no arrow to draw
+                    if line_label.label.msg.is_none() {
+                        continue
+                    }
                     if !self.config.compact {
                         // Margin alternate
                         write_margin(