[cmds] Modernize codebase by replacing NULL with nullptr

Fixes -Wzero-as-null-pointer-constant warning.

Test: m
Bug: 68236239
Change-Id: I1635395d653ace5a11c75795f4a7d2bf2d9e0b1b
Merged-In: I73a0a82e3e32001f8ffb0880250c7023dd8290d3
11 files changed