Mysqld crashes after hold f5 in browser
The important part of that log is

InnoDB: mmap(137363456 bytes) failed; errno 12 - ENOMEM 12 /* Out of memory */

If you check system log you will see OOM killer doing its work too.

It means your browser sends multiple requests when you hold F5, they probably are executing slowly so they stack, the web server eats more and more memory for each new request and after some time there is just not enough so some process has to be killed - that victim is the mysqld server process which holds some big buffers (key buffer and/or innodb buffer pool).

Then it cannot start anymore until some memory is freed (for example by restarting the system or the web server service).

Check this guide to set your MySQL server to use less memory or separate web and db servers.