EntryElement UITextField position miscalculated

When testing an app that uses an EntryElement on an Ad-Hoc configuration (couldn't reproduce it in Debug), after a while (usually the 2nd or 3rd time loading a dialog) the static UIFont that is used to calculate the EntryAligment returns a font of size 0. So it messes up all the calculations for the ComputeEntryPosition method.

Using a local UIFont var fixes the problem.

I think this could be a problem of the mono compiler, but at least this patch fixes the issue for MT.D. 

Hope it helps!

PS. system info below
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Xamarin Studio
Version 4.0.3 (build 13)
Installation UUID: 675af92b-4382-4a2c-aeb5-2718b3d00757
Runtime:
	Mono 3.0.7 (master/514fcd7)
	GTK 2.24.16
	GTK# (2.12.0.0)
	Package version: 300070000

Apple Developer Tools
Xcode 4.6.1 (2067)
Build 4H512

Xamarin.iOS
Version: 6.3.2.0 (Indie Edition)
Hash: 56e611b
Branch: 
Build date: 2013-25-03 21:37:44-0400
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