[Canvas] Font picker can't handle custom fonts

[rashmivkulkarni]

Kibana version: 6.5.0 BC1

**Elasticsearch version:**6.5.0 BC1

Server OS version: CentOS 7

Browser version: Chrome

Browser OS version: CentOS

Original install method (e.g. download page, yum, from source, etc.): BC1

Describe the bug: when you import a JSON file into ur workpad, and click on one of the element, the following error is being captured in console

TypeError: Cannot read property 'inputDisplay' of undefined
    at EuiSuperSelectControl (vendors.bundle.js:102)
    at beginWork (vendors.bundle.js:208)
    at e (vendors.bundle.js:208)
    at f (vendors.bundle.js:208)
    at G (vendors.bundle.js:208)
    at x (vendors.bundle.js:208)
    at n (vendors.bundle.js:208)
    at interactiveUpdates (vendors.bundle.js:208)
    at Wd (vendors.bundle.js:208)
bf @ vendors.bundle.js:208
commitErrorLogging @ vendors.bundle.js:208
R @ vendors.bundle.js:208
G @ vendors.bundle.js:208
x @ vendors.bundle.js:208
n @ vendors.bundle.js:208
interactiveUpdates @ vendors.bundle.js:208
Wd @ vendors.bundle.js:208

cc @cqliu1

[cqliu1]

The issue was that this workpad uses custom fonts that aren't in the list of available fonts in Canvas used to populate the font picker.

[stacey-gammon]

Is the only issue the error being logged @Rasroh? If so I don't think this qualifies as a blocker. Going to remove that label, please let me know if you disagree!