Set "WhiteColors" as palette id for host palette if no id is provided (#395)

* Change files

* Remove change file

* Set "WhiteColors" as palette id if no id is provided

* Change files

* Create helper function for palette cache key

change/@uifabricshared-theming-react-native-2020-08-12-17-25-28-colorsFix.json

@@ -0,0 +1,8 @@
+{
+  "type": "patch",
+  "comment": "Set \"WhiteColors\" as palette id if no id is provided",
+  "packageName": "@uifabricshared/theming-react-native",
+  "email": "krsiler@microsoft.com",
+  "dependentChangeType": "patch",
+  "date": "2020-08-13T00:25:28.785Z"
+}

packages/framework/theming-react-native/src/NativeModule/ThemingModuleHelpers.ts

@@ -32,8 +32,12 @@ function updatePaletteInCache(module: IOfficeThemingModule, cache: PaletteCache,
   }
 }
 
+const getPaletteCacheKey = (palette?: string) => {
+  return useFakePalette ? 'debug' : palette || 'WhiteColors';
+};
+
 function translatePalette(module: IOfficeThemingModule, paletteCache: PaletteCache, palette?: string): IPartialPalette {
-  const key = useFakePalette ? 'debug' : palette || 'WhiteColors';
+  const key = getPaletteCacheKey(palette);
   if (!paletteCache[key]) {
     updatePaletteInCache(module, paletteCache, key);
   }
@@ -52,7 +56,7 @@ export function translateOfficeTheme(module: IOfficeThemingModule, cache: Palett
     },
     typography: module.fluentTypography,
     host: {
-      palette: cache[id]
+      palette: cache[getPaletteCacheKey(id)]
     }
   };
 }