fixes #502

Author: wumpz

src/main/java/net/sf/jsqlparser/expression/ExpressionVisitorAdapter.java

@@ -227,7 +227,7 @@ public void visit(SubSelect subSelect) {
 
     @Override
     public void visit(CaseExpression expr) {
-        if (expr.getSwitchExpression()!=null) {
+        if (expr.getSwitchExpression() != null) {
             expr.getSwitchExpression().accept(this);
         }
         for (Expression x : expr.getWhenClauses()) {
@@ -296,7 +296,9 @@ public void visit(Modulo expr) {
 
     @Override
     public void visit(AnalyticExpression expr) {
-        expr.getExpression().accept(this);
+        if (expr.getExpression() != null) {
+            expr.getExpression().accept(this);
+        }
         expr.getDefaultValue().accept(this);
         expr.getOffset().accept(this);
         if (expr.getKeep() != null) {

src/test/java/net/sf/jsqlparser/expression/ExpressionVisitorAdapterTest.java

@@ -209,5 +209,12 @@ public void testCaseWithoutElse3() throws JSQLParserException {
         ExpressionVisitorAdapter adapter = new ExpressionVisitorAdapter();
         expr.accept(adapter);
     }
+    
+    @Test
+    public void testAnalyticFunctionWithoutExpression502() throws JSQLParserException {
+        Expression expr = CCJSqlParserUtil.parseExpression("row_number() over (order by c)");
+        ExpressionVisitorAdapter adapter = new ExpressionVisitorAdapter();
+        expr.accept(adapter);
+    }
 
 }