[AndroidSdkWindows] Guard against exception checking registry (#79)

Fixes: https://developercommunity.visualstudio.com/content/problem/883179/ilegal-characters-in-path-after-fresh-install.html

Somehow, a registry key contains invalid path characters.
This causes an `ArgumentException` from
`AndroidSdkWindows.CheckRegistryKeyForExecutable()`:

	System.ArgumentException: Illegal characters in path.
	   at System.IO.Path.CheckInvalidPathChars(String path, Boolean checkAdditional)
	   at System.IO.Path.Combine(String path1, String path2)
	   at Xamarin.Android.Tools.AndroidSdkWindows.CheckRegistryKeyForExecutable(UIntPtr key, String subkey, String valueName, Wow64 wow64, String subdir, String exe)
	   at Xamarin.Android.Tools.AndroidSdkWindows.<GetAllAvailableAndroidSdks>d__37.MoveNext()
	   at System.Linq.Enumerable.<DistinctIterator>d__64`1.MoveNext()
	   at System.Linq.Buffer`1..ctor(IEnumerable`1 source)
	   at System.Linq.Enumerable.ToArray[TSource](IEnumerable`1 source)
	   at Xamarin.Android.Tools.AndroidSdkBase.get_AllAndroidSdks()
	   at Xamarin.Android.Tools.AndroidSdkBase.Initialize(String androidSdkPath, String androidNdkPath, String javaSdkPath)
	   at Xamarin.Android.Tools.AndroidSdkWindows.Initialize(String androidSdkPath, String androidNdkPath, String javaSdkPath)
	   at Xamarin.Android.Tools.AndroidSdkInfo..ctor(Action`2 logger, String androidSdkPath, String androidNdkPath, String javaSdkPath)

Handle the `ArgumentException` by wrapping the body of
`CheckRegistryKeyForExecutable()` within a `try/catch` block and
catch all exceptions.  If an exception is thrown, there is no
executable of interest.

src/Xamarin.Android.Tools.AndroidSdk/Sdks/AndroidSdkWindows.cs

@@ -303,19 +303,23 @@ public override void SetPreferredAndroidNdkPath (string path)
 		#region Helper Methods
 		private static bool CheckRegistryKeyForExecutable (UIntPtr key, string subkey, string valueName, RegistryEx.Wow64 wow64, string subdir, string exe)
 		{
-			string key_name = string.Format (@"{0}\{1}\{2}", key == RegistryEx.CurrentUser ? "HKCU" : "HKLM", subkey, valueName);
+			try {
+				string key_name = string.Format (@"{0}\{1}\{2}", key == RegistryEx.CurrentUser ? "HKCU" : "HKLM", subkey, valueName);
 
-			var path = NullIfEmpty (RegistryEx.GetValueString (key, subkey, valueName, wow64));
+				var path = NullIfEmpty (RegistryEx.GetValueString (key, subkey, valueName, wow64));
 
-			if (path == null) {
-				return false;
-			}
+				if (path == null) {
+					return false;
+				}
 
-			if (!ProcessUtils.FindExecutablesInDirectory (Path.Combine (path, subdir), exe).Any ()) {
+				if (!ProcessUtils.FindExecutablesInDirectory (Path.Combine (path, subdir), exe).Any ()) {
+					return false;
+				}
+
+				return true;
+			} catch (Exception) {
 				return false;
 			}
-
-			return true;
 		}
 		#endregion