Unexpected exit when clicking "Clusters" button in Single Axis section

When I was trying to click the button "Clusters" in the Single Axis section, program exited with a bug report:

Process: MemAxes [4273]
Path: /Users/USER/*/MemAxes.app/Contents/MacOS/MemAxes
Identifier: ???
Version: ??? (???)
Code Type: X86-64 (Native)
Parent Process: ??? [1]
Responsible: MemAxes [4273]
User ID: 501

Date/Time: 2015-10-12 02:28:53.151 -0700
OS Version: Mac OS X 10.11 (15A284)
Report Version: 11
Anonymous UUID: 5028DC7D-5B3D-4144-90D7-CE5204A8E2A6

Sleep/Wake UUID: 9995E98F-551A-4A89-8A90-D6FD98F5212E

Time Awake Since Boot: 120000 seconds
Time Since Wake: 6300 seconds

System Integrity Protection: enabled

Crashed Thread: 0 Dispatch queue: com.apple.main-thread

Exception Type: EXC_CRASH (SIGABRT)
Exception Codes: 0x0000000000000000, 0x0000000000000000
Exception Note: EXC_CORPSE_NOTIFY

Application Specific Information:
terminating with uncaught exception of type std::out_of_range: vector
abort() called

Reproduce the crash in the MemAxes application by clicking "Clusters" in the Single Axis section on macOS. Use the reported std::out_of_range exception from vector as the starting point for investigation; done means the button no longer exits unexpectedly.

Written by the indexing model from the issue text.