fix NPE reported by Curt Arnold

git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@278239 13f79535-47bb-0310-9956-ffa450edef68

WHATSNEW

@@ -204,6 +204,9 @@ Fixed bugs:
 
 * DirectoryScanner.slowScan() was broken. Bugzilla report 34722.
 
+* DirectoryScanner.scan() could throw a NullPointerException on
+  case-insensitive filesystems (read Windows or MacOS X).
+
 Other changes:
 --------------
 

src/main/org/apache/tools/ant/DirectoryScanner.java

@@ -872,7 +872,7 @@ public class DirectoryScanner
                 }
                 if ((myfile == null || !myfile.exists()) && !isCaseSensitive()) {
                     File f = findFile(basedir, currentelement, false);
-                    if (f.exists()) {
+                    if (f != null && f.exists()) {
                         // adapt currentelement to the case we've
                         // actually found
                         currentelement = FILE_UTILS.removeLeadingPath(basedir,