Prevent merge if it's 'this'

de4dot.code/renamer/ExistingNames.cs

@@ -62,6 +62,8 @@ namespace de4dot.code.renamer {
 		}
 
 		public void Merge(ExistingNames other) {
+			if (this == other)
+				return;
 			foreach (var key in other.allNames.Keys)
 				allNames[key] = true;
 		}

de4dot.code/renamer/TypeNames.cs

@@ -113,6 +113,8 @@ namespace de4dot.code.renamer {
 		protected abstract string FixName(string prefix, string name);
 
 		public virtual TypeNames Merge(TypeNames other) {
+			if (this == other)
+				return this;
 			foreach (var pair in other.typeNames) {
 				NameCreator nc;
 				if (typeNames.TryGetValue(pair.Key, out nc))

de4dot.code/renamer/VariableNameState.cs

@@ -61,6 +61,8 @@ namespace de4dot.code.renamer {
 		}
 
 		public VariableNameState Merge(VariableNameState other) {
+			if (this == other)
+				return this;
 			existingVariableNames.Merge(other.existingVariableNames);
 			existingMethodNames.Merge(other.existingMethodNames);
 			existingPropertyNames.Merge(other.existingPropertyNames);