[gimp] app: free an unusing allocated string when not used as a result.

[Jehan <jehanp src gnome org>]

commit 025cebf76f6d9366695ff76cd959140c9c0385c7
Author: Jehan <jehan girinstud io>
Date:   Fri Aug 20 21:53:41 2021 +0200

    app: free an unusing allocated string when not used as a result.
    
    Another leak reported by Massimo.

 app/propgui/gimppropgui-eval.c | 4 ++++
 1 file changed, 4 insertions(+)
---
diff --git a/app/propgui/gimppropgui-eval.c b/app/propgui/gimppropgui-eval.c
index 719e500866..548bc1adc8 100644
--- a/app/propgui/gimppropgui-eval.c
+++ b/app/propgui/gimppropgui-eval.c
@@ -730,6 +730,10 @@ gimp_prop_eval_string_selection (GObject      *config,
               match  = TRUE;
               result = value;
             }
+          else
+            {
+              g_free (value);
+            }
 
           if (! g_strcmp0 (*t, ","))
             {