Memory Leak and Slow IDE When Editing Very Long .md files

I've got a really long readme in node.  WebStorm is dead slow when it gets so long.  And...I eventually got this error below, any way I can resolve this issue?  

I'm using:

WebStorm 2018.1.2
Build #WS-181.4668.60, built on April 23, 2018
JRE: 1.8.0_152-release-1136-b29 x86_64
macOS 10.13.4

I took a look at https://intellij-support.jetbrains.com/hc/en-us/community/posts/115000013384-IntelliJ-Idea-2016-memory-problems-on-OSX but when I tried adding this:

vcs.log.index.git=off

I get this warning: