Due to a problem in the Intel® Quartus® Prime Pro Edition software version 20.4 and earlier, you may see this fatal error message in block diagram when when you right click on the symbol > Symbol Properties > Format: Untick the "No Fill" option.
*** Fatal Error: Segment Violation: faulting address=(nil), PC=0x2aaae498eba6 : 0x2aaae498eba6: edt_gdlgq!GDLGQ_FORMAT_PAGE::set_properties(GIOQ_OBJECT*) 0x3e8
Module: quartus
Stack Trace:
Err Handler 0x10123: ERR_UNWINDER_BACKTRACE::get_stack_trace(void const**, int, int, void*) 0xf3 (ccl_err)
Err Handler 0x73768: msg_ie_get_call_stack(void*) 0xe9 (ccl_msg)
Err Handler 0x74c64: MSG_INTERNAL_ERROR::report_fatal(char const*, void*) 0x3c (ccl_msg)
This problem is fixed beginning with the Intel® Quartus® Prime Pro edition software 21.1.