Render the else block in sections if the path does not exist or if the path can't be walked.

This fixes all existing compliance tests.

src/bin.rs

@@ -65,11 +65,7 @@ fn read_context_from_stdin() -> serde_json::Value {
         .read_to_string(&mut buffer)
         .expect("Failed to read stdin");
 
-    let parsed: serde_json::Value = serde_json::from_str(&buffer).expect("Failed to parse json");
-    match parsed {
-        serde_json::Value::Object(obj) => serde_json::value::Value::Object(obj),
-        _ => panic!("Expected context to be an object"),
-    }
+    serde_json::from_str(&buffer).expect("Failed to parse json")
 }
 
 impl ContextElement for serde_json::Value {}
@@ -112,7 +108,10 @@ impl Walkable for serde_json::Value {
                 segment: segment.to_string(),
                 elem: self,
             }),
-            serde_json::Value::Array(_arr) => todo!("Arrays not supported yet"),
+            serde_json::Value::Array(_arr) => Err(RenderError::CantWalk {
+                segment: segment.to_string(),
+                elem: self,
+            }),
             serde_json::Value::Object(obj) => {
                 obj.get(segment)
                     .map(|val| val as _)