avoid crashing with empty build templates

This would occur if e.g. only the profession was given.

2 files changed, 14 insertions, 8 deletions

diff --git a/src/main.rs b/src/main.rs
index d928c09..6194ef0 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -226,8 +226,8 @@ fn validate_legend(input: String) -> Result<(), String> {
 fn run() -> MainResult<()> {
     let matches = App::new(APP_NAME)
         .version("0.1")
-        .author("Daniel <kingdread@gmx.de>")
-        .about("Renders GW2 skills and traits.")
+        .author("Peter Parker IV")
+        .about("Renders Guild Wars 2 skills and traits.")
         .arg(
             Arg::with_name("profession")
                 .help("Selects which profession to use.")
@@ -304,12 +304,12 @@ fn run() -> MainResult<()> {
     }
 
     let mut renderer = render::Renderer::new(&mut api, Default::default());
-    let img = renderer.render_buildtemplate(&build).unwrap();
-    let filename = matches.value_of("outfile").unwrap();
-    img.save(filename)?;
-
-    if !matches.is_present("quiet") {
-        println!("Image saved in {}", filename);
+    if let Ok(img) = renderer.render_buildtemplate(&build) {
+        let filename = matches.value_of("outfile").unwrap();
+        img.save(filename)?;
+        if !matches.is_present("quiet") {
+            println!("Image saved in {}", filename);
+        }
     }
 
     Ok(())
diff --git a/src/render.rs b/src/render.rs
index bb38399..90eff14 100644
--- a/src/render.rs
+++ b/src/render.rs
@@ -19,6 +19,9 @@ quick_error! {
             cause(err)
             from()
         }
+        EmptyBuild {
+            description("The build template contains nothing worth rendering")
+        }
     }
 }
 
@@ -284,6 +287,9 @@ impl<'r> Renderer<'r> {
         build: &BuildTemplate,
     ) -> Result<RgbaImage, RenderError> {
         let images = self.construct_parts(build)?;
+        if images.is_empty() {
+            return Err(RenderError::EmptyBuild);
+        }
         self.merge_parts(&images)
     }