fixes #449

Author: wumpz

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

@@ -227,11 +227,15 @@ public void visit(SubSelect subSelect) {
 
     @Override
     public void visit(CaseExpression expr) {
-        expr.getSwitchExpression().accept(this);
+        if (expr.getSwitchExpression()!=null) {
+            expr.getSwitchExpression().accept(this);
+        }
         for (Expression x : expr.getWhenClauses()) {
             x.accept(this);
         }
-        expr.getElseExpression().accept(this);
+        if (expr.getElseExpression() != null) {
+            expr.getElseExpression().accept(this);
+        }
     }
 
     @Override

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

@@ -188,5 +188,26 @@ public void testSubSelectExpressionProblem() throws JSQLParserException {
             fail();
         }
     }
+    
+    @Test
+    public void testCaseWithoutElse() throws JSQLParserException {
+        Expression expr = CCJSqlParserUtil.parseExpression("CASE WHEN 1 then 0 END");
+        ExpressionVisitorAdapter adapter = new ExpressionVisitorAdapter();
+        expr.accept(adapter);
+    }
+    
+    @Test
+    public void testCaseWithoutElse2() throws JSQLParserException {
+        Expression expr = CCJSqlParserUtil.parseExpression("CASE WHEN 1 then 0 ELSE -1 END");
+        ExpressionVisitorAdapter adapter = new ExpressionVisitorAdapter();
+        expr.accept(adapter);
+    }
+    
+    @Test
+    public void testCaseWithoutElse3() throws JSQLParserException {
+        Expression expr = CCJSqlParserUtil.parseExpression("CASE 3+4 WHEN 1 then 0 END");
+        ExpressionVisitorAdapter adapter = new ExpressionVisitorAdapter();
+        expr.accept(adapter);
+    }
 
 }