pull

1 files changed, 2 insertions, 2 deletions

diff --git a/src/client/util/SelectionManager.ts b/src/client/util/SelectionManager.ts
index 730db4f29..7795a4a59 100644
--- a/src/client/util/SelectionManager.ts
+++ b/src/client/util/SelectionManager.ts
@@ -73,8 +73,8 @@ export namespace SelectionManager {
     // computed functions, such as used in IsSelected generate errors if they're called outside of a
     // reaction context.  Specifying the context with 'outsideReaction' allows an efficiency feature
     // to avoid unnecessary mobx invalidations when running inside a reaction.
-    export function IsSelected(doc: DocumentView, outsideReaction?: boolean): boolean {
-        return outsideReaction ?
+    export function IsSelected(doc: DocumentView | undefined, outsideReaction?: boolean): boolean {
+        return !doc ? false : outsideReaction ?
             manager.SelectedDocuments.get(doc) ? true : false : // get() accesses a hashtable -- setting anything in the hashtable generates a mobx invalidation for every get()
             computedFn(function isSelected(doc: DocumentView) {  // wraapping get() in a computedFn only generates mobx() invalidations when the return value of the function for the specific get parameters has changed
                 return manager.SelectedDocuments.get(doc) ? true : false;