refactor: show clear exception when failed to eval valid color scheme

Author: WhiredPlanck

app/src/main/java/com/osfans/trime/data/theme/ColorManager.kt

@@ -137,7 +137,8 @@ object ColorManager {
         when {
             followSystemDayNight -> if (isNightMode) darkModeColorScheme else lightModeColorScheme
             else -> null
-        } ?: colorScheme(normalModeColor) ?: colorScheme("default")!!
+        } ?: colorScheme(normalModeColor) ?: colorScheme("default")
+            ?: throw IllegalArgumentException("Failed to evaluate valid color scheme")
 
     /** 每次切换主题后，都要调用此函数，初始化配色 */
     fun switchTheme(theme: Theme) {