Fix for emoji keyboard UI artifact (while fast scrolling)

[yshubin]

This change fixed UI issue (#221) for fast scrolling (inside emoji keyboard)

Code changes

We just checking if lazy drawable initialization for EmojiImageView already was completed.

[vanniktech]

Sorry this took forever. I'll merge once CI has approved it.

[codecov]

Codecov Report

Merging #223 into master will not change coverage.
The diff coverage is 0%.

@@           Coverage Diff           @@
##           master     #223   +/-   ##
=======================================
  Coverage   28.04%   28.04%           
=======================================
  Files          22       22           
  Lines         820      820           
  Branches       90       90           
=======================================
  Hits          230      230           
  Misses        571      571           
  Partials       19       19

Impacted Files	Coverage Δ
...main/java/com/vanniktech/emoji/EmojiImageView.java	0% <0%> (ø)	⬆️

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