Fix viewgrp, viewatt, viewscore, delstudent bugs

[neoruien]

Fixed parsing and viewing bugs related to the following commands:

• viewgrp
• viewatt
• viewscore
• delstudent

[codecov-io]

Codecov Report

Merging #196 into master will increase coverage by 0.11%.
The diff coverage is 40.00%.

@@             Coverage Diff              @@
##             master     #196      +/-   ##
============================================
+ Coverage     48.30%   48.41%   +0.11%     
  Complexity      783      783              
============================================
  Files           155      155              
  Lines          3857     3856       -1     
  Branches        477      471       -6     
============================================
+ Hits           1863     1867       +4     
- Misses         1850     1851       +1     
+ Partials        144      138       -6     

Impacted Files	Coverage Δ	Complexity Δ
...am/serenity/logic/parser/ViewAttCommandParser.java	0.00% <0.00%> (ø)	0.00 <0.00> (ø)
...am/serenity/logic/parser/ViewGrpCommandParser.java	0.00% <0.00%> (ø)	0.00 <0.00> (ø)
.../serenity/logic/parser/ViewScoreCommandParser.java	0.00% <0.00%> (ø)	0.00 <0.00> (ø)
.../logic/parser/student/DelStudentCommandParser.java	80.76% <100.00%> (+24.10%)	7.00 <0.00> (ø)

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