Display empty values when marking "Show defaults"

Previously `false` and `0` were ignored even when "Show defaults"
checkbox was marked.

Bug: 176906864
Test: build winscope, take a trace, mark show defaults, check if false
values appear on the property list

Change-Id: Ia114eea91c677e92f0bf4edd4a9e9107e014d90e
1 file changed