--- calibre-5.12.0/src/calibre/utils/formatter.py.orig	2021-03-06 21:06:44.587932763 +0100
+++ calibre-5.12.0/src/calibre/utils/formatter.py	2021-03-06 21:07:14.202470086 +0100
@@ -656,8 +656,8 @@
 
     def do_node_first_non_empty(self, prog):
         for expr in prog.expression_list:
-            if v := self.expr(expr):
-                return v
+            if self.expr(expr):
+                return self.expr(expr)
         return ''
 
     def do_node_for(self, prog):