NH-2038 - Fix SqlStringHelper.RemoveAsAliasesFromSql method when alias is not present on a string

Author: hazzik

src/NHibernate.Test/NHSpecificTest/NH2318/Fixture.cs

@@ -56,7 +56,7 @@ public void CriteriaTrimFunctionsWithParameters()
                             "trim",
                             NHibernateUtil.String,
                             Projections.Constant("f"),
-                            Projections.SqlProjection("from as literal", null, null), // Silly hack to get "from" as a second argument.
+                            Projections.SqlProjection("from", null, null), // Silly hack to get "from" as a second argument.
                             Projections.Property("Name")),
                         "irst"));
                 IList<A> items = criteria.List<A>();

src/NHibernate/SqlCommand/SqlStringHelper.cs

@@ -44,7 +44,9 @@ public static SqlString[] Add(SqlString[] x, string sep, SqlString[] y)
 
 		public static SqlString RemoveAsAliasesFromSql(SqlString sql)
 		{
-			return sql.Substring(0, sql.LastIndexOfCaseInsensitive(" as "));
+			int index = sql.LastIndexOfCaseInsensitive(" as ");
+			if (index < 0) return sql;
+			return sql.Substring(0, index);
 		}