chore: avoid to panic in case of an entity attribute is not found

01.workspace/heave/src/str/entity.rs

@@ -141,14 +141,15 @@ impl Entity {
     /// # Returns
     ///
     /// A `Result<T, FailedTo>` which is `Ok(T)` if the conversion is successful,
-    /// or `Err(FailedTo::ConvertValue)` if it fails.
+    /// or `Err(FailedTo::ConvertValue)` if the conversion fails,
+    /// or `Err(FailedTo::FindAttribute)` if the attribute doesn't exist.
     pub fn unwrap<T>(&self, id: &str) -> Result<T, FailedTo>
     where
         T: TryFrom<Value>,
     {
         self.value_of(id)
             .map(|value| T::try_from(value.clone()).map_err(|_| FailedTo::ConvertValue))
-            .unwrap()
+            .unwrap_or(Err(FailedTo::FindAttribute))
     }
     /// Unwraps an attribute's value into an `Option<T>`.
     ///

01.workspace/heave/src/str/failed_to.rs

@@ -13,6 +13,8 @@ pub enum FailedTo {
     ConvertValue,
     /// Failed to execute predicate to mutate an item.
     ExecutePredicate(Vec<Box<dyn error::Error>>),
+    /// Failed to find given attribute.
+    FindAttribute,
     /// Failed to initialize the database.
     InitDatabase,
     /// Failed to load data from the database.
@@ -38,6 +40,7 @@ impl PartialEq for FailedTo {
                 | (FailedTo::ConvertObject, FailedTo::ConvertObject)
                 | (FailedTo::ConvertValue, FailedTo::ConvertValue)
                 | (FailedTo::ExecutePredicate(_), FailedTo::ExecutePredicate(_))
+                | (FailedTo::FindAttribute, FailedTo::FindAttribute)
                 | (FailedTo::InitDatabase, FailedTo::InitDatabase)
                 | (FailedTo::LoadFromDB, FailedTo::LoadFromDB)
                 | (FailedTo::LockCatalog, FailedTo::LockCatalog)
@@ -74,6 +77,7 @@ impl std::fmt::Display for FailedTo {
                 }
                 Ok(())
             }
+            FailedTo::FindAttribute => write!(f, "Failed to find given attribute"),
             FailedTo::InitDatabase => write!(f, "Failed to initialize the database"),
             FailedTo::LoadFromDB => write!(f, "Failed to load data from the database"),
             FailedTo::LockCatalog => {