[gnome-calculator] Fixed compile error

[Robert Roth <robertroth src gnome org>]

commit 1b9cf01c02e9a3008c47e3c1fb8a6441e7c0b2cf
Author: Robert Roth <robert roth off gmail com>
Date:   Mon Aug 1 09:53:05 2022 +0300

    Fixed compile error

 src/math-popover.vala | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/src/math-popover.vala b/src/math-popover.vala
index 2906782e..b0a8ef87 100644
--- a/src/math-popover.vala
+++ b/src/math-popover.vala
@@ -23,7 +23,7 @@ public abstract class MathPopover<T> : Gtk.Popover
         this.equation = equation;
         this.model = model;
         this.compare_func = (a,b) => compare_func(a,b);
-        this.changed_handler = function_name_entry.changed.connect (name_entry_changed_cb);
+        this.changed_handler = name_entry ().changed.connect (name_entry_changed_cb);
     }
 
     protected abstract Gtk.Entry name_entry ();