Correct the error type.

Author: MathieuDutSik

linera-execution/src/execution.rs

@@ -320,9 +320,7 @@ where
                         // For composed operations, use the result from the last operation
                         let previous_results = txn_tracker.previous_operation_results();
                         if previous_results.is_empty() {
-                            return Err(ExecutionError::InternalError(
-                                "Composed operation requires a previous operation result, but none found"
-                            ));
+                            return Err(ExecutionError::ComposedOperationCannotBeFirst);
                         }
                         // Get the last operation result as input
                         previous_results.last().unwrap().clone()

linera-execution/src/lib.rs

@@ -211,7 +211,8 @@ pub enum ExecutionError {
     DecompressionError(#[from] DecompressionError),
     #[error("The given promise is invalid or was polled once already")]
     InvalidPromise,
-
+    #[error("Composed operation cannot be first")]
+    ComposedOperationCannotBeFirst,
     #[error("Attempted to perform a reentrant call to application {0}")]
     ReentrantCall(ApplicationId),
     #[error(