Add a default value for coloringsPresentOnTree

There is a default value set in modifyControlsStateViaTree, but this is
the only property that doesn't have an explicit default set by
getDefaultControlsState. Add it for consistency.

src/reducers/controls.ts

@@ -44,7 +44,7 @@ export interface BasicControlsState {
   canTogglePanelLayout: boolean
   colorBy: string
   colorByConfidence: boolean
-  coloringsPresentOnTree?: Set<string>
+  coloringsPresentOnTree: Set<string>
   colorScale?: ColorScale
   dateMax: string
   dateMaxNumeric: number
@@ -142,6 +142,7 @@ export const getDefaultControlsState = (): ControlsState => {
     colorBy: defaults.colorBy,
     colorByConfidence: false,
     colorScale: undefined,
+    coloringsPresentOnTree: new Set(),
     explodeAttr: undefined,
     selectedBranchLabel: "none",
     showAllBranchLabels: false,