track preconditions (#99)

Author: ay42

Sources/Grid/Styles/Layout/LayoutMath.swift

@@ -17,6 +17,7 @@ func tracksCount(tracks: Tracks, spacing: CGFloat, availableLength: CGFloat) ->
  case .count(let count):
  return count
  case .fixed(let length):
+ precondition(length > 0, "Minimum track length should be greated than 0")
  let columnCount = Int(availableLength / length)
 
  for columns in (0...columnCount).reversed() {
@@ -26,8 +27,9 @@ func tracksCount(tracks: Tracks, spacing: CGFloat, availableLength: CGFloat) ->
  }
  }
  return 1
- case .min(let minWidth):
- let columnCount = Int(availableLength / minWidth)
+ case .min(let length):
+ precondition(length > 0, "Minimum track length should be greated than 0")
+ let columnCount = Int(availableLength / length)
 
  for columns in (0...columnCount).reversed() {
  let suggestedItemWidth = itemLength(tracksCount: columns, spacing: spacing, availableLength: availableLength)