Add a check to make sure we have results.

Author: Paul van Brenk

src/services/services.ts

@@ -3573,14 +3573,16 @@ module ts {
 
         function getOccurrencesAtPosition(fileName: string, position: number): ReferenceEntry[] {
             let results = getOccurrencesAtPositionCore(fileName, position);
-
-            let sourceFile = getCanonicalFileName(normalizeSlashes(fileName));
-
-            // ensure the results are in the file we're interested in
-            results.forEach((value) => {
-                let targetFile = getCanonicalFileName(normalizeSlashes(value.fileName));
-                Debug.assert(sourceFile == targetFile, `Unexpected file in results. Found results in ${targetFile} expected only results in ${sourceFile}.`);
-            });
+            
+            if (results) {
+                let sourceFile = getCanonicalFileName(normalizeSlashes(fileName));
+
+                // ensure the results are in the file we're interested in
+                results.forEach((value) => {
+                    let targetFile = getCanonicalFileName(normalizeSlashes(value.fileName));
+                    Debug.assert(sourceFile == targetFile, `Unexpected file in results. Found results in ${targetFile} expected only results in ${sourceFile}.`);
+                });
+            }
 
             return results;
         }