Fix suggestion bugs

[AudreyFelicio]

No description provided.

[codecov-io]

Codecov Report

Merging #261 into master will decrease coverage by 0.37%.
The diff coverage is 53.00%.

@@             Coverage Diff              @@
##             master     #261      +/-   ##
============================================
- Coverage     60.48%   60.11%   -0.38%     
- Complexity      809      818       +9     
============================================
  Files           127      127              
  Lines          3189     3244      +55     
  Branches        422      447      +25     
============================================
+ Hits           1929     1950      +21     
- Misses         1124     1132       +8     
- Partials        136      162      +26     

Impacted Files	Coverage Δ	Complexity Δ
...du/stock/logic/parser/SuggestionCommandParser.java	75.62% <52.52%> (-7.39%)	79.00 <31.00> (+8.00)	⬇️
.../seedu/stock/logic/commands/SuggestionCommand.java	58.33% <100.00%> (ø)	3.00 <0.00> (ø)
.../main/java/seedu/stock/logic/parser/CliSyntax.java	74.62% <0.00%> (+2.98%)	11.00% <0.00%> (+1.00%)

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[kaichaoang]

LGTM!