Fix to #30115 - IndexOutOfRangeException in CreateNavigationExpansionExpression(Expression sourceExpression, IEntityType entityType) / get_Chars(Int32 index) when EF class named "<>f__AnonymousType01Child" in 7.0.2 version

Check if ShortName returns empty string, and if so use token parameter name.

Fixes #30115

Author: maumar

src/EFCore/Query/Internal/NavigationExpandingExpressionVisitor.cs

@@ -1947,7 +1947,12 @@ private NavigationExpansionExpression CreateNavigationExpansionExpression(
         PopulateEagerLoadedNavigations(entityReference.IncludePaths);
 
         var currentTree = new NavigationTreeExpression(entityReference);
-        var parameterName = GetParameterName(entityType.ShortName()[0].ToString().ToLowerInvariant());
+
+        var entityTypeName = entityType.ShortName();
+        var parameterName = GetParameterName(
+            string.IsNullOrEmpty(entityTypeName)
+                ? "e"
+                : entityTypeName[0].ToString().ToLowerInvariant());
 
         return new NavigationExpansionExpression(sourceExpression, currentTree, currentTree, parameterName);
     }