Fix mode icon sharing in modes list

Modes sharing the same icon would also share the applied tint (e.g. all with the "active" tint even if only the last one of them is active).

(Although it should never happen, also removed a potential NPE for mode icons without ConstantState).

Fixes: 367131481
Test: manual
Flag: android.app.modes_ui
Change-Id: I56867783310ea57f2e92c866ff0b5b53ac86bf37