Handle matching no switches.

org_mode_samples/lesser_element/lesser_block/example/space_for_parameters.org

@@ -0,0 +1,2 @@
+#+begin_example 
+#+end_example

src/compare/diff.rs

@@ -1559,12 +1559,20 @@ fn compare_example_block<'b, 's>(
 
     // Compare switches
     let switches = get_property_quoted_string(emacs, ":switches")?;
-    if switches.as_ref().map(String::as_str) != rust.switches {
-        this_status = DiffStatus::Bad;
-        message = Some(format!(
-            "Switches mismatch (emacs != rust) {:?} != {:?}",
-            switches, rust.switches
-        ));
+    match (switches.as_ref().map(String::as_str), rust.switches) {
+        (None, None) => {}
+        (Some(""), None) => {}
+        (None, Some("")) => {
+            unreachable!("The organic parser would return a None instead of an empty string.");
+        }
+        (Some(e), Some(r)) if e == r => {}
+        _ => {
+            this_status = DiffStatus::Bad;
+            message = Some(format!(
+                "Switches mismatch (emacs != rust) {:?} != {:?}",
+                switches, rust.switches
+            ));
+        }
     }
 
     // Compare number-lines

src/parser/lesser_block.rs

@@ -326,6 +326,7 @@ fn _lesser_block_begin<'b, 'g, 'r, 's, 'c>(
     Ok((remaining, name))
 }
 
+#[derive(Debug)]
 struct ExampleSwitches<'s> {
     source: &'s str,
     number_lines: Option<SwitchNumberLines>,
@@ -334,6 +335,7 @@ struct ExampleSwitches<'s> {
     label_format: Option<&'s str>,
 }
 
+#[derive(Debug)]
 enum SwitchState {
     Normal,
     NewLineNumber,