do not calculate favicon color on manual icon replace

classes/pref/feeds.php

@@ -500,14 +500,8 @@ class Pref_Feeds extends Handler_Protected {
 				if ($this->dbh->num_rows($result) != 0) {
 					@unlink(ICONS_DIR . "/$feed_id.ico");
 					if (rename($icon_file, ICONS_DIR . "/$feed_id.ico")) {
-
-						require_once "colors.php";
-
-						$favicon_color = $this->dbh->escape_string(
-							calculate_avg_color(ICONS_DIR . "/$feed_id.ico"));
-
 						$this->dbh->query("UPDATE ttrss_feeds SET
-							favicon_avg_color = '$favicon_color'
+							favicon_avg_color = ''
 							WHERE id = '$feed_id'");
 
 						$rc = 0;