Freron MailMate

MailMate (1.13.2 on Mojave) suddenly crashes upon startup.

It first started while running (crash log follows), and now I can't run it (and have only my iPhone and a shell window running Mutt to access my mail...).

Process: MailMate [84580]
Path: /Applications/MailMate.app/Contents/MacOS/MailMate
Identifier: com.freron.MailMate
Version: 1.13.2 (5712)
Code Type: X86-64 (Native)
Parent Process: ??? [1]
Responsible: MailMate [84580]
User ID: 502

Date/Time: 2020-08-31 13:53:03.036 +0200
OS Version: Mac OS X 10.15.6 (19G2021)
Report Version: 12
Anonymous UUID: E35993D5-B78C-06D2-D225-828681310821

Sleep/Wake UUID: 871870DF-9069-4943-9922-70F7039A453D

Time Awake Since Boot: 640000 seconds
Time Since Wake: 22000 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:
abort() called

Thread 0 Crashed:: Dispatch queue: com.apple.main-thread
0 libsystem_kernel.dylib 0x00007fff67ce533a pthread_kill + 10
1 libsystem_pthread.dylib 0x00007fff67da1e60 pthread_kill + 430
2 libsystem_c.dylib 0x00007fff67c6c808 abort + 120
3 com.freron.MailMate 0x000000010ccb4e9f atomic_saving::atomic_saving_t::add_file(std::1::basic_string, std::__1::allocator > const&, atomic_saving::data_t const&) + 527
4 com.freron.MailMate 0x000000010ccb50ac atomic_saving::atomic_saving_t::add_file(std::__1::basic_string, std::__1::allocator > const&, std::__1::basic_string, std::__1::allocator >&) + 56
5 com.freron.MailMate 0x000000010ccb52d7 atomic_saving::atomic_saving_t::set_file(std::__1::basic_string, std::__1::allocator > const&, std::__1::basic_string, std::__1::allocator >&) + 85
6 com.freron.MailMate 0x000000010cad9e4d database_t::delete_message(int) + 457
7 com.freron.MailMate 0x000000010cada135 delete_timer_callback(database_t*) + 119
8 com.apple.CoreFoundation 0x00007fff2db32d52 CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION + 17
9 com.apple.CoreFoundation 0x00007fff2db32cf1 __CFRunLoopDoSource0 + 103
10 com.apple.CoreFoundation 0x00007fff2db32b0b __CFRunLoopDoSources0 + 209
11 com.apple.CoreFoundation 0x00007fff2db3183a __CFRunLoopRun + 927
12 com.apple.CoreFoundation 0x00007fff2db30e3e CFRunLoopRunSpecific + 462
13 com.freron.MailMate 0x000000010c9cee7a -[OakWebView contentRuleList] + 721

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