fix

com.unity.uiwidgets/Runtime/material/bottom_app_bar_theme.cs

         public static BottomAppBarTheme lerp(BottomAppBarTheme a, BottomAppBarTheme b, float t) {
             return new BottomAppBarTheme(
                 color: Color.lerp(a?.color, b?.color, t),
-                elevation: MathUtils.lerpNullableFloat(a?.elevation ?? 0.0f, b?.elevation ?? 0.0f, t),
+                elevation: MathUtils.lerpNullableFloat(a?.elevation, b?.elevation, t),
                 shape: t < 0.5f ? a?.shape : b?.shape
             );
         }

com.unity.uiwidgets/Runtime/material/slider_theme.cs

             D.assert(a != null);
             D.assert(b != null);
             return new SliderThemeData(
-                trackHeight: MathUtils.lerpNullableFloat(a.trackHeight.Value, b.trackHeight.Value, t),
+                trackHeight: MathUtils.lerpNullableFloat(a.trackHeight, b.trackHeight, t),
                 activeTrackColor: Color.lerp(a.activeTrackColor, b.activeTrackColor, t),
                 inactiveTrackColor: Color.lerp(a.inactiveTrackColor, b.inactiveTrackColor, t),
                 disabledActiveTrackColor: Color.lerp(a.disabledActiveTrackColor, b.disabledActiveTrackColor, t),