Fix renamed variable that was breaking support for channelled spells.

diff --git a/OvaleBestAction.lua b/OvaleBestAction.lua
index b6e2f8b..4d4bf08 100644
--- a/OvaleBestAction.lua
+++ b/OvaleBestAction.lua
@@ -273,7 +273,7 @@ local function ComputeFunction(element)
 							start = tickTime
 							break
 						end
-						tickTime = tickTime + tickLength
+						tickTime = tickTime + tick
 					end
 					Ovale:Logf("%s start=%f, numTicks=%d, tick=%f, tickTime=%f", spellId, start, numTicks, tick, tickTime)
 				end