Index: src/wp-admin/includes/plugin-install.php
===================================================================
--- src/wp-admin/includes/plugin-install.php	(revision 29867)
+++ src/wp-admin/includes/plugin-install.php	(working copy)
@@ -326,6 +326,10 @@
 function install_plugin_information() {
 	global $tab;
 
+	if ( empty( $_REQUEST['plugin'] ) ) {
+		return;
+	}
+
 	$api = plugins_api( 'plugin_information', array(
 		'slug' => wp_unslash( $_REQUEST['plugin'] ),
 		'is_ssl' => is_ssl(),