lightdm-webkit2-greeter: silence error message on some systems

the greeter searches for backgrounds in /usr/share/backgrounds,
if the dir doesn't exists it uses a fallback image.
Some change in lightdm ended up printing an error message if the
background dir wasn't existing

srcpkgs/lightdm-webkit2-greeter/patches/04-do-not-print-any-non-critical-errors-as-erros.patch

@@ -0,0 +1,18 @@
+Lightdm seems to show a error popup once a greeter even prints the word error,
+but does not even print the full log line.
+So just change an ERROR to warn and encude the error message as bas64,
+the default theme handles this kind of error just fine.
+
+---
+--- web-greeter-2.2.5/src/gresource/js/ThemeUtils.js	2017-04-24 21:51:30.000000000 +0200
++++ ThemeUtils.js	2022-02-03 01:21:13.467417715 +0100
+@@ -142,7 +142,8 @@
+ 			return __ThemeUtils.dirlist( path );
+ 
+ 		} catch( err ) {
+-			console.log( `[ERROR] theme_utils.dirlist(): ${err}` );
++			err = btoa(unescape(encodeURIComponent(err)));
++			console.log( `[WARN] theme_utils.dirlist(): ${err} (base64 to not trip lightdm up)` );
+ 			return [];
+ 		}
+ 	}

srcpkgs/lightdm-webkit2-greeter/template

@@ -1,7 +1,7 @@
 # Template file for 'lightdm-webkit2-greeter'
 pkgname=lightdm-webkit2-greeter
 version=2.2.5
-revision=2
+revision=3
 wrksrc="web-greeter-${version}"
 build_style=meson
 hostmakedepends="pkg-config glib-devel"