fix(muscript): use flatMap

muscript-runtime/src/main/java/io/gitlab/jfronny/muscript/runtime/Runtime.java

@@ -227,7 +227,7 @@ public class Runtime {
                         Dynamic lv = evaluate(e.callable(), scope);
                         if (Dynamic.isNull(lv)) throw locationalException(expr, "Cannot invoke null");
                         dc = lv.asCallable();
-                        arg = of(e.arguments().stream().map(a -> evaluate(a, scope)).toArray(Dynamic[]::new));
+                        arg = of(e.arguments().stream().flatMap(a -> evaluate(a, scope)).toArray(Dynamic[]::new));
                     } catch (RuntimeException ex) {
                         throw locationalException(expr, "Could not perform call successfully", ex);
                     }