Fixing a null exception error when bound tables are null. (#1327)

* Fixing a null exception error when bound tables are null.

* skipping star expansion when there is no active conn

* Fixing a comment

src/Microsoft.SqlTools.ServiceLayer/LanguageServices/AutoCompleteHelper.cs

@@ -754,6 +754,15 @@ namespace Microsoft.SqlTools.ServiceLayer.LanguageServices
                 starObjectIdentifier = (SqlObjectIdentifier)selectStarExpression.Children.ElementAt(0);
             }
 
+            /*
+            Returning no suggestions when the bound tables are null. 
+            This happens when there are no existing connections for the script. 
+            */
+            if (selectStarExpression.BoundTables == null)
+            {
+                return null;
+            }
+
             List<ITabular> boundedTableList = selectStarExpression.BoundTables.ToList();
 
             IList<string> columnNames = new List<string>();

src/Microsoft.SqlTools.ServiceLayer/LanguageServices/LanguageService.cs

@@ -1659,12 +1659,18 @@ namespace Microsoft.SqlTools.ServiceLayer.LanguageServices
             this.currentCompletionParseInfo = scriptParseInfo;
             resultCompletionItems = result.CompletionItems;
  
-            // Expanding star expressions in query
+            /*
+             Expanding star expressions in query only when the script is connected to a database
+             as the parser requires a connection to determine column names 
+            */
+            if (connInfo != null)
+            {
                 CompletionItem[] starExpansionSuggestion = AutoCompleteHelper.ExpandSqlStarExpression(scriptDocumentInfo);
                 if (starExpansionSuggestion != null)
                 {
                     return starExpansionSuggestion;
                 }
+            }
 
             // if there are no completions then provide the default list
             if (resultCompletionItems == null)