address a few possible exceptions

Author: retailcoder

Rubberduck.CodeAnalysis/Inspections/Concrete/AssignmentNotUsedInspection.cs

@@ -131,20 +131,19 @@ private static IEnumerable<AssignmentNode> FindUnusedAssignmentNodes(INode node,
                                                             .Contains(refNode));
 
                 var assignmentsPrecedingReference = assignmentExprNodesWithReference.Any()
-                    ? assignmentExprNodes.TakeWhile(n => n != assignmentExprNodesWithReference.Last())
-                                                .Last()
-                                                .Nodes(new[] { typeof(AssignmentNode) })
+                    ? assignmentExprNodes.TakeWhile(n => n != assignmentExprNodesWithReference.LastOrDefault())
+                                                ?.LastOrDefault()
+                                                ?.Nodes(new[] { typeof(AssignmentNode) })
                     : allAssignmentsAndReferences.TakeWhile(n => n != refNode)
                         .OfType<AssignmentNode>();
 
-                if (assignmentsPrecedingReference.Any())
+                if (assignmentsPrecedingReference?.Any() ?? false)
                 {
-                    usedAssignments.Add(assignmentsPrecedingReference.Last() as AssignmentNode);
+                    usedAssignments.Add(assignmentsPrecedingReference.LastOrDefault() as AssignmentNode);
                 }
             }
 
-            return allAssignmentsAndReferences.OfType<AssignmentNode>()
-                                                .Except(usedAssignments);
+            return allAssignmentsAndReferences.OfType<AssignmentNode>().Except(usedAssignments);
         }
 
         private static bool IsDescendentOfNeverFlagNode(AssignmentNode assignment)

Rubberduck.Parsing/VBA/DeclarationCaching/DeclarationFinder.cs

@@ -333,7 +333,7 @@ public IEnumerable<ModuleBodyElementDeclaration> FindEventHandlers(Declaration e
         {
             var withEventsDeclarations = FindWithEventFields(eventDeclaration);
             return withEventsDeclarations
-                .Select(withEventsField => FindHandlersForWithEventsField(withEventsField).Single(handler => 
+                .Select(withEventsField => FindHandlersForWithEventsField(withEventsField).SingleOrDefault(handler => 
                     handler.IdentifierName.Equals($"{withEventsField.IdentifierName}_{eventDeclaration.IdentifierName}", StringComparison.InvariantCultureIgnoreCase)));
         }
 
@@ -362,9 +362,10 @@ public ICollection<Declaration> FindFormEventHandlers()
         /// </summary>
         /// <param name="name">The identifier name of the project declaration to find.</param>
         /// <param name="result">The <see cref="ProjectDeclaration"/> result, if found; null otherwise.</param>
-        public bool TryFindProjectDeclaration(string name, out Declaration result)
+        /// <param name="includeUserDefined">True to include user-defined projects in the search; false by default.</param>
+        public bool TryFindProjectDeclaration(string name, out Declaration result, bool includeUserDefined = false)
         {
-            result = _projects.Value.SingleOrDefault(project => project.IdentifierName.Equals(name, StringComparison.InvariantCultureIgnoreCase) && !project.IsUserDefined);
+            result = _projects.Value.FirstOrDefault(project => project.IdentifierName.Equals(name, StringComparison.InvariantCultureIgnoreCase) && project.IsUserDefined == includeUserDefined);
             return result != null;
         }