Fix random bugs

[kevinchangjk]

Actually just fixed a bunch of the remaining bugs from PE-D.

• Fixes [PE-D][Tester C] Wrong error returned for invalid rate command #183
• Fixes [PE-D][Tester D] Math not parsed #167
• Fixes [PE-D][Tester A] JAR File: Trying to view an employee that is clearly present by employee ID fails. #197
• Fixes [PE-D][Tester D] Leave table is not fully visible #198
• Fixes [PE-D][Tester C] Wrong exception given for delete command #199

[prit3010]

LGTM

[codecov-commenter]

Codecov Report

Merging #262 (6cb374c) into master (270492e) will not change coverage.
The diff coverage is 83.33%.

@@            Coverage Diff            @@
##             master     #262   +/-   ##
=========================================
  Coverage     65.21%   65.21%           
  Complexity      604      604           
=========================================
  Files            93       93           
  Lines          2199     2199           
  Branches        271      271           
=========================================
  Hits           1434     1434           
  Misses          687      687           
  Partials         78       78           

Impacted Files	Coverage Δ
src/main/java/coydir/commons/core/Messages.java	0.00% <ø> (ø)
...c/main/java/coydir/logic/commands/ViewCommand.java	0.00% <0.00%> (ø)
...in/java/coydir/logic/commands/AddLeaveCommand.java	100.00% <100.00%> (ø)
...main/java/coydir/logic/commands/DeleteCommand.java	100.00% <100.00%> (ø)
...java/coydir/logic/commands/DeleteLeaveCommand.java	80.00% <100.00%> (ø)
...c/main/java/coydir/logic/commands/EditCommand.java	95.87% <100.00%> (ø)
...c/main/java/coydir/logic/commands/RateCommand.java	92.00% <100.00%> (ø)

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[chao890]

Lousy. Merge approved.