fix: continue on empty line

src/error.rs

@@ -1,3 +1,4 @@
 pub enum ShellError {
+    EmptyLine,
     Execute(String),
 }

src/execute.rs

@@ -5,6 +5,9 @@ use crate::error::ShellError::Execute;
 use crate::parse::parse_line;
 
 pub fn interpret(line: &str) -> Result<(), ShellError> {
+    if line.is_empty() {
+        return Err(ShellError::EmptyLine);
+    }
     let (keyword, args) = parse_line(line);
 
     let mut command = Command::new(keyword);

src/main.rs

@@ -21,6 +21,9 @@ fn main() -> Result<()> {
         match readline {
             Ok(line) => match interpret(&line) {
                 Ok(_) => {}
+                Err(ShellError::EmptyLine) => {
+                    continue;
+                }
                 Err(ShellError::Execute(err)) => {
                     eprintln!("{}", err)
                 }