Evas textblock: Fix crash when cutting ligatures with formats.

"f<color=#f00>i</color>f" could cause textblock to crash. It doesn't
crash anymore. It doesn't render the colours correctly either, but at
least this is the first step.

This is the start of fixing T1308

@bugfix

src/lib/evas/common/evas_text_utils.c

@@ -180,6 +180,10 @@ evas_common_text_props_index_find(const Evas_Text_Props *props, int _cutoff)
    int max = props->len - 1;
    int mid;
 
+   /* Props can be empty, verify they are not before going on. */
+   if (!props->info)
+      return -1;
+
    _cutoff += props->text_offset;
    ot_info = props->info->ot + props->start;
    /* Should get us closer to the right place. */

src/tests/evas/evas_test_textblock.c

@@ -2612,6 +2612,9 @@ START_TEST(evas_textblock_formats)
    evas_object_textblock_text_markup_prepend(cur, "<b></b>");
    ck_assert_str_eq(evas_object_textblock_text_markup_get(tb), "ab<b></b>c<br/>def");
 
+   /* Ligatures cut by formats */
+   evas_object_textblock_text_markup_set(tb, "f<color=#f00>i</color>f");
+   evas_object_textblock_size_formatted_get(tb, NULL, NULL);
 
    END_TB_TEST();
 }