Fix #2342: Do not generate empty names for foreach loop variables.

ICSharpCode.Decompiler/IL/Transforms/AssignVariableNames.cs

@@ -18,6 +18,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Diagnostics;
 using System.Linq;
 using System.Reflection;
 using System.Reflection.Metadata;
@@ -473,6 +474,7 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 				reservedVariableNames.Add(proposedName, 0);
 			}
 			int count = ++reservedVariableNames[proposedName];
+			Debug.Assert(!string.IsNullOrWhiteSpace(proposedName));
 			if (count > 1)
 			{
 				return proposedName + count.ToString();
@@ -763,6 +765,7 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 				reservedVariableNames.Add(proposedName, 0);
 			}
 			int count = ++reservedVariableNames[proposedName];
+			Debug.Assert(!string.IsNullOrWhiteSpace(proposedName));
 			if (count > 1)
 			{
 				return proposedName + count.ToString();
@@ -815,6 +818,7 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 				reservedVariableNames.Add(proposedName, 0);
 			}
 			int count = ++reservedVariableNames[proposedName];
+			Debug.Assert(!string.IsNullOrWhiteSpace(proposedName));
 			if (count > 1)
 			{
 				return proposedName + count.ToString();
@@ -828,7 +832,7 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 		private static bool IsPlural(string baseName, ref string proposedName)
 		{
 			var newName = Vocabularies.Default.Singularize(baseName, inputIsKnownToBePlural: false);
-			if (newName == baseName)
+			if (string.IsNullOrWhiteSpace(newName) || newName == baseName)
 				return false;
 			proposedName = newName;
 			return true;