fix: Fix comparison bug when allocating all balances of the farming pool

[hallazzang]

Description

closes: #134

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[codecov]

Codecov Report

Merging #135 (e9445ec) into master (c73ffe5) will not change coverage.
The diff coverage is 100.00%.

❗ Current head e9445ec differs from pull request most recent head a3b073c. Consider uploading reports for the commit a3b073c to get more accurate results

@@           Coverage Diff           @@
##           master     #135   +/-   ##
=======================================
  Coverage   69.71%   69.71%           
=======================================
  Files          25       25           
  Lines        2262     2262           
=======================================
  Hits         1577     1577           
  Misses        533      533           
  Partials      152      152           

Impacted Files	Coverage Δ
x/farming/keeper/reward.go	88.42% <100.00%> (ø)

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[dongsam]

LGTM