Fix duplicated signature when using Back button in Chrome (#5809)

CHANGELOG

@@ -29,6 +29,7 @@ CHANGELOG Roundcube Webmail
 - Allow contacts without an email address (#5079)
 - Localized timezone selector (#4983)
 - Use 7bit encoding for ISO-2022-* charsets in sent mail (#5640)
+- Fix duplicated signature when using Back button in Chrome (#5809)
 - Fix touch event issue on messages list in IE/Edge (#5781)
 - Fix so links over images are not removed in plain text signatures converted from HTML (#4473)
 - Fix various issues when downloading files with names containing non-ascii chars, use RFC 2231 (#5772)

program/js/app.js

@@ -4211,6 +4211,11 @@ function rcube_webmail()
     }
 
     if (!html_mode) {
+      // On Back button Chrome will overwrite textarea with old content
+      // causing e.g. the same signature is added twice (#5809)
+      if (input_message.value && input_message.defaultValue !== undefined)
+        input_message.value = input_message.defaultValue;
+
       pos = this.env.top_posting && this.env.compose_mode ? 0 : input_message.value.length;
 
       // add signature according to selected identity