Index: src/wp-includes/capabilities.php
===================================================================
--- src/wp-includes/capabilities.php	(revision 32522)
+++ src/wp-includes/capabilities.php	(working copy)
@@ -1098,7 +1098,7 @@
 		break;
 	case 'delete_post':
 	case 'delete_page':
-		$post = get_post( $args[0] );
+		$post = ( isset( $args[0] ) ) ? get_post( $args[0] ) : get_post();
 
 		if ( 'revision' == $post->post_type ) {
 			$post = get_post( $post->post_parent );
@@ -1142,9 +1142,11 @@
 		// edit_others_posts
 	case 'edit_post':
 	case 'edit_page':
-		$post = get_post( $args[0] );
-		if ( empty( $post ) )
+		$post = ( isset( $args[0] ) ) ? get_post( $args[0] ) : get_post();
+
+		if ( empty( $post ) ) {
 			break;
+		}
 
 		if ( 'revision' == $post->post_type ) {
 			$post = get_post( $post->post_parent );
@@ -1155,8 +1157,9 @@
 		if ( ! $post_type->map_meta_cap ) {
 			$caps[] = $post_type->cap->$cap;
 			// Prior to 3.1 we would re-call map_meta_cap here.
-			if ( 'edit_post' == $cap )
+			if ( 'edit_post' == $cap ) {
 				$cap = $post_type->cap->$cap;
+			}
 			break;
 		}
 
@@ -1186,7 +1189,7 @@
 		break;
 	case 'read_post':
 	case 'read_page':
-		$post = get_post( $args[0] );
+		$post = ( isset( $args[0] ) ) ? get_post( $args[0] ) : get_post();
 
 		if ( 'revision' == $post->post_type ) {
 			$post = get_post( $post->post_parent );
@@ -1197,8 +1200,9 @@
 		if ( ! $post_type->map_meta_cap ) {
 			$caps[] = $post_type->cap->$cap;
 			// Prior to 3.1 we would re-call map_meta_cap here.
-			if ( 'read_post' == $cap )
+			if ( 'read_post' == $cap ) {
 				$cap = $post_type->cap->$cap;
+			}
 			break;
 		}
 
@@ -1217,7 +1221,8 @@
 		}
 		break;
 	case 'publish_post':
-		$post = get_post( $args[0] );
+		$post = ( isset( $args[0] ) ) ? get_post( $args[0] ) : get_post();
+
 		$post_type = get_post_type_object( $post->post_type );
 
 		$caps[] = $post_type->cap->publish_posts;
@@ -1225,7 +1230,8 @@
 	case 'edit_post_meta':
 	case 'delete_post_meta':
 	case 'add_post_meta':
-		$post = get_post( $args[0] );
+		$post = ( isset( $args[0] ) ) ? get_post( $args[0] ) : get_post();
+
 		$caps = map_meta_cap( 'edit_post', $user_id, $post->ID );
 
 		$meta_key = isset( $args[ 1 ] ) ? $args[ 1 ] : false;