Since dependencies must be arrays, ensure they are if not a callable.

In set_dependencies, if the first argument is not a callable,
cast it to an array when we assign it to the class property.

In get_dependencies, cast the return value to an array.

Issue: #37

Author: Camwyn

src/Assets/Asset.php

@@ -878,7 +878,7 @@ public function get_dependencies(): array {
 			);
 		}
 
-		return $dependencies;
+		return (array) $dependencies;
 	}
 
 	/**
@@ -1791,7 +1791,7 @@ public function set_dependencies( ...$dependencies ) {
 		if ( $dependencies[0] && is_callable( $dependencies[0] ) ) {
 			$this->dependencies = $dependencies[0];
 		} else {
-			$this->dependencies = $dependencies;
+			$this->dependencies = (array) $dependencies;
 		}
 
 		return $this;