Fix bugs pertaining to PE-D

[ethan-goh]

• Fixed a bug where the PersonDetails panel did not clear upon calling the clear command
• Fixed a bug where if more than one whitespace was present between modules or before modules in the EditCommand for editing modules, the command did not run

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Files with missing lines	Coverage Δ	Complexity Δ
...ava/seedu/address/logic/commands/ClearCommand.java	100.00% <100.00%> (ø)	2.00 <0.00> (ø)
.../seedu/address/logic/parser/EditCommandParser.java	100.00% <100.00%> (ø)	17.00 <0.00> (ø)

[JYL27]

LGTM