avoid crashing with empty build templates

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

1 files changed, 6 insertions, 0 deletions

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)
     }