Fix #2210: Fix undoing the checkmark bug.

uhabits-android/src/main/java/org/isoron/uhabits/activities/habits/list/views/NumberButtonView.kt

@@ -174,11 +174,11 @@ class NumberButtonView(
         fun draw(canvas: Canvas) {
             val activeColor = when {
                 value < 0.0 -> lowContrast
+                (targetType == AT_LEAST) && ((value == 0.0) && (threshold != 0.0)) -> lowContrast
                 (targetType == AT_LEAST) && (value >= threshold) -> color
                 (targetType == AT_MOST) && (value <= threshold) -> color
                 else -> mediumContrast
             }
-
             val label: String
             val typeface: Typeface
             val textSize: Float