Prevent a NPE when using groupBy with an attribute in ERXQuery by ini…

…tializing the array in constructor like groupingKeys.

Frameworks/Core/ERExtensions/Sources/er/extensions/eof/ERXQuery.java

@@ -311,6 +311,7 @@ protected ERXQuery() {
 		// Set defaults
 		fetchKeys = new NSMutableArray<>();
 		groupingKeys = new NSMutableArray<>();
+		groupingAttributes = new NSMutableArray<>();
 		orderings = new NSMutableArray<>();
 		refreshRefetchedObjects = false;
 		usesDistinct = false;
@@ -1275,7 +1276,6 @@ protected void computeSelectAndGroupingAttributes() {
 		// Initialize arrays for storing the select attributes, 
 		// grouping attributes and sort orderings
 		selectAttributes = new NSMutableArray<>(20);
-		groupingAttributes = new NSMutableArray<>(20);
 
 		// This keeps track of EOAttribute objects used
 		attributesByName = new NSMutableDictionary<>();