fix: set variables command and add debug to auth

`envx set key=value` now works when the project has no variables (in
this case, it used to break because the helper function decrypt_full_many
would return an error)

`envx auth` now has a `--debug` flag to print the request and response

src/commands/auth.rs

@@ -12,6 +12,10 @@ pub struct Args {
     /// Key to sign with
     #[clap(short, long)]
     key: Option<String>,
+
+    /// Debug output
+    #[clap(short, long)]
+    debug: bool,
 }
 
 pub async fn command(args: Args) -> anyhow::Result<()> {
@@ -30,12 +34,22 @@ pub async fn command(args: Args) -> anyhow::Result<()> {
 
     println!("auth token:\n{}", auth_token.signature);
 
+    let url = format!("{}test-auth", get_api_url());
+
+    if args.debug {
+        dbg!(&url);
+    }
+
     let res = client
-        .post(format!("{}/test-auth", get_api_url()))
+        .post(url)
         .header(header::AUTHORIZATION, format!("Bearer {}", auth_token))
         .send()
         .await?;
 
+    if args.debug {
+        dbg!(&res);
+    }
+
     let status = res.status();
 
     if status.is_success() {

src/utils/rpgp.rs

@@ -210,7 +210,12 @@ pub fn decrypt_full_many(
     messages: Vec<String>,
     config: &Config,
 ) -> Result<Vec<String>, anyhow::Error> {
-    let first = messages.first().ok_or_else(|| anyhow!("No messages"))?;
+    let first = if let Some(first) = messages.first() {
+        first
+    } else {
+        return Ok(vec![]);
+    };
+
     let msg = Message::from_string(first.as_str())?.0;
 
     let recipients: Vec<String> = msg