diff --git a/IDCBrowser/IDCBrowser.py b/IDCBrowser/IDCBrowser.py
index 52287e1..039c584 100644
--- a/IDCBrowser/IDCBrowser.py
+++ b/IDCBrowser/IDCBrowser.py
@@ -846,6 +846,11 @@ def collectionSelected(self, item):
     self.clearStudiesTableWidget()
     self.clearSeriesTableWidget()
     self.selectedCollection = item
+
+    # Check if a valid collection is selected
+    if not self.selectedCollection:
+      return
+
     cacheFile = self.cachePath + self.selectedCollection + '.json'
     self.progressMessage = "Getting available patients for collection: " + self.selectedCollection