Fix NPE on custom exceptions

pmd-apex/src/main/java/net/sourceforge/pmd/lang/apex/rule/codestyle/FormalParameterRegexNamingConventionsRule.java

@@ -31,6 +31,11 @@ public class FormalParameterRegexNamingConventionsRule extends AbstractRegexNami
 
     @Override
     public Object visit(ASTParameter node, Object data) {
+        // classes that extend Exception will contains methods that have parameters with null names
+        if (node.getImage() == null) {
+            return data;
+        }
+
         if (node.getModifiers().isFinal()) {
             checkMatches(FINAL_METHOD_PARAMETER_REGEX, node, data);
         } else {

pmd-apex/src/test/resources/net/sourceforge/pmd/lang/apex/rule/codestyle/xml/FormalParameterRegexNamingConventions.xml

@@ -57,4 +57,12 @@ public class Foo {
         ]]></code>
     </test-code>
 
+    <test-code>
+        <description>ignores null parameter names</description>
+        <expected-problems>0</expected-problems>
+        <code><![CDATA[
+public with sharing class MyException extends Exception { }
+        ]]></code>
+    </test-code>
+
 </test-data>