[gnc-plugin-page-report] plug char* leaks

also move a few lines later to avoid confirming double filepath !=
nullptr confirmation

gnucash/gnome/gnc-plugin-page-report.cpp

@@ -1604,12 +1604,6 @@ gnc_get_export_filename (SCM choice, GtkWindow *parent)
     filepath = gnc_file_dialog (parent, title, nullptr, default_dir,
                                 GNC_FILE_DIALOG_EXPORT);
 
-    if (filepath != nullptr) // test for cancel pressed
-    {
-        /* Try to test for extension on file name, add if missing */
-        if (g_strrstr(filepath, ".") == nullptr)
-            filepath = g_strconcat(filepath, ".", g_ascii_strdown(type, strlen(type)), nullptr);
-    }
     g_free (type);
     g_free (title);
     g_free (default_dir);
@@ -1617,6 +1611,16 @@ gnc_get_export_filename (SCM choice, GtkWindow *parent)
     if (!filepath)
         return nullptr;
 
+    /* Try to test for extension on file name, add if missing */
+    if (strchr (filepath, '.') == nullptr)
+    {
+        char* extension = g_ascii_strdown (type, -1);
+        char* newpath = g_strdup_printf ("%s.%s", filepath, extension);
+        g_free (extension);
+        g_free (filepath);
+        filepath = newpath;
+    }
+
     default_dir = g_path_get_dirname(filepath);
     gnc_set_default_directory (GNC_PREFS_GROUP_REPORT, default_dir);
     g_free(default_dir);