Fix error when using useFluent method from Vue 2

[Demivan]

fixes #611

[codecov]

Codecov Report

Merging #612 (5efdff1) into develop (38897a8) will increase coverage by 2.01%.
The diff coverage is 90.90%.

@@             Coverage Diff             @@
##           develop     #612      +/-   ##
===========================================
+ Coverage    76.20%   78.22%   +2.01%     
===========================================
  Files           11       11              
  Lines          248      248              
  Branches        43       42       -1     
===========================================
+ Hits           189      194       +5     
+ Misses          43       38       -5     
  Partials        16       16              

Flag	Coverage Δ
vue-2	73.38% <90.90%> (+2.01%)	⬆️
vue-3	72.58% <90.90%> (+2.01%)	⬆️

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Impacted Files	Coverage Δ
packages/fluent-vue/src/vue/component.ts	92.59% <75.00%> (+3.70%)	⬆️
packages/fluent-vue/src/composition.ts	75.00% <100.00%> (+9.09%)	⬆️

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