Fix crash showing tooltip when mouse was on the edge between two tabs

src/main/kotlin/net/shadowfacts/cacao/geometry/Rect.kt

@@ -35,7 +35,7 @@ data class Rect(val left: Double, val top: Double, val width: Double, val height
 	}
 
 	operator fun contains(point: Point): Boolean {
-		return point.x in left..right && point.y in top..bottom
+		return point.x >= left && point.x < right && point.y >= top && point.y < bottom
 	}
 
 }