The gtk_entry_set_text routine checks if the val is NULL and if so that routine returns, so it is expected to call it with a NULL value and if that happens gtk_entry_set_text correctly returns.

Adding -DG_DISABLE_CHECKS makes g_return_[vak_]if_fail not to be checked. That makes gtk_entry_set_text to behave different if -DG_DISABLE_CHECKS is provided or not, leading to a segfault of gtk even if gtk_entry_set_text has an explicit check of the text argument.

Because of that I'd say even that evolution is not right calling gtk_entry_set_text with a NULL argument I'd say that gtk shouldn't segfault when in gtk_entry_set_text there's has a protection to check if the argument is NULL.