Bug 797566 - Crash on use of context menu in importer

If the context menu key is used on the "Assign transfer account page"
the application will crash. This was down to the call back function
gnc_gen_trans_onPopupMenu_cb being defined with a second parameter of
GdkEvent but it should not have, removing this fixes the bug.

gnucash/import-export/import-main-matcher.c

@@ -124,7 +124,6 @@ static gboolean gnc_gen_trans_onButtonPressed_cb (
                     GNCImportMainMatcher *info);
 static gboolean gnc_gen_trans_onPopupMenu_cb (
                     GtkTreeView *treeview,
-                    GdkEvent *event,
                     GNCImportMainMatcher *info);
 static void refresh_model_row (
                     GNCImportMainMatcher *gui,
@@ -651,7 +650,6 @@ gnc_gen_trans_onButtonPressed_cb (GtkTreeView *treeview,
 
 static gboolean
 gnc_gen_trans_onPopupMenu_cb (GtkTreeView *treeview,
-                              GdkEvent *event,
                               GNCImportMainMatcher *info)
 {
     GtkTreeSelection *selection;