[evolution] Event with empty summary can cause crash

[Milan Crha <mcrha src gnome org>]

commit 2aa2017bf991b3e9eea0660b648d6383b826ebab
Author: Milan Crha <mcrha redhat com>
Date:   Mon Jan 7 14:31:26 2019 +0100

    Event with empty summary can cause crash
    
    In case libical is compiled to keep properties with empty values,
    which means icalproperty_get_xxxx() can return NULL instead of an empty
    string, the code of the ECellText (aka the List View) could try
    to use the NULL value in strcmp(), strlen() and such, which causes
    abort of the application.
    
    This had been reported downstream as:
    https://bugzilla.redhat.com/show_bug.cgi?id=1658002

 src/calendar/gui/e-cal-model.c | 2 +-
 src/e-util/e-cell-text.c       | 8 ++++----
 2 files changed, 5 insertions(+), 5 deletions(-)
---
diff --git a/src/calendar/gui/e-cal-model.c b/src/calendar/gui/e-cal-model.c
index d15a6d6201..78bf368f18 100644
--- a/src/calendar/gui/e-cal-model.c
+++ b/src/calendar/gui/e-cal-model.c
@@ -436,7 +436,7 @@ get_summary (ECalModelComponent *comp_data)
        icalproperty *prop;
 
        prop = icalcomponent_get_first_property (comp_data->icalcomp, ICAL_SUMMARY_PROPERTY);
-       if (prop)
+       if (prop && icalproperty_get_summary (prop))
                return g_strdup (icalproperty_get_summary (prop));
 
        return g_strdup ("");
diff --git a/src/e-util/e-cell-text.c b/src/e-util/e-cell-text.c
index de1b147187..5c5be50a99 100644
--- a/src/e-util/e-cell-text.c
+++ b/src/e-util/e-cell-text.c
@@ -307,7 +307,7 @@ ect_stop_editing (ECellTextView *text_view,
                ECellView *ecell_view = (ECellView *) text_view;
                ECellText *ect = (ECellText *) ecell_view->ecell;
 
-               if (strcmp (old_text, text)) {
+               if (g_strcmp0 (old_text, text)) {
                        e_cell_text_set_value (
                                ect, ecell_view->e_table_model,
                                model_col, row, text);
@@ -628,7 +628,7 @@ generate_layout (ECellTextView *text_view,
 
        if (row >= 0) {
                gchar *temp = e_cell_text_get_text (ect, ecell_view->e_table_model, model_col, row);
-               layout = build_layout (text_view, row, temp ? temp : "?", width);
+               layout = build_layout (text_view, row, temp ? temp : "", width);
                e_cell_text_free_text (ect, ecell_view->e_table_model, model_col, temp);
        } else
                layout = build_layout (text_view, row, "Mumbo Jumbo", width);
@@ -810,7 +810,7 @@ ect_draw (ECellView *ecell_view,
        layout = generate_layout (text_view, model_col, view_col, row, x2 - x1);
 
        if (edit && edit->view_col == view_col && edit->row == row) {
-               layout = layout_with_preedit  (text_view, row, edit->text ? edit->text : "?",  x2 - x1);
+               layout = layout_with_preedit  (text_view, row, edit->text ? edit->text : "",  x2 - x1);
        }
 
        cairo_move_to (cr, x_origin, y_origin);
@@ -1218,7 +1218,7 @@ ect_enter_edit (ECellView *ecell_view,
        edit->default_cursor_shown = TRUE;
 
        temp = e_cell_text_get_text (ect, ecell_view->e_table_model, model_col, row);
-       edit->old_text = g_strdup (temp);
+       edit->old_text = g_strdup (temp ? temp : "");
        e_cell_text_free_text (ect, ecell_view->e_table_model, model_col, temp);
        edit->text = g_strdup (edit->old_text);