Fix NullPointerException when File#listFiles() returns null

See issue 1934 where the NPE is listed in a few comments. The problem is
that File#listFiles() can return null, see documentation:

http://docs.oracle.com/javase/7/docs/api/java/io/File.html#listFiles%28%29

This fixes all the listFiles call sites that aren't part of an assertion
in a test case.

Author: robinst

java/client/src/org/openqa/selenium/io/FileHandler.java

@@ -129,8 +129,11 @@ public static boolean delete(File toDelete) {
     boolean deleted = true;
 
     if (toDelete.isDirectory()) {
-      for (File child : toDelete.listFiles()) {
-        deleted &= child.canWrite() && delete(child);
+      File[] children = toDelete.listFiles();
+      if (children != null) {
+        for (File child : children) {
+          deleted &= child.canWrite() && delete(child);
+        }
       }
     }
 

java/client/src/org/openqa/selenium/io/Zip.java

@@ -93,8 +93,11 @@ private void zip(File inputDir, OutputStream writeTo) throws IOException {
 
   private void addToZip(String basePath, ZipOutputStream zos, File toAdd) throws IOException {
     if (toAdd.isDirectory()) {
-      for (File file : toAdd.listFiles()) {
-        addToZip(basePath, zos, file);
+      File[] files = toAdd.listFiles();
+      if (files != null) {
+        for (File file : files) {
+          addToZip(basePath, zos, file);
+        }
       }
     } else {
       FileInputStream fis = new FileInputStream(toAdd);

java/client/test/com/thoughtworks/selenium/InternalSelenseTestBase.java

@@ -88,10 +88,13 @@ public static void buildJavascriptLibraries() throws IOException {
       }
       File atomsDir = InProject.locate("build/javascript/selenium-atoms");
 
-      for (File file : atomsDir.listFiles()) {
-        if (file.getName().endsWith(".js")) {
-          File dest = new File(buildDir, file.getName());
-          Files.copy(file, dest);
+      File[] atomsFiles = atomsDir.listFiles();
+      if (atomsFiles != null) {
+        for (File file : atomsFiles) {
+          if (file.getName().endsWith(".js")) {
+            File dest = new File(buildDir, file.getName());
+            Files.copy(file, dest);
+          }
         }
       }
 
@@ -100,10 +103,13 @@ public static void buildJavascriptLibraries() throws IOException {
 
       File seDir = InProject.locate("java/client/test/com/thoughtworks/selenium");
       File destDir = InProject.locate("java/client/build/production/com/thoughtworks/selenium");
-      for (File file : seDir.listFiles()) {
-        if (file.getName().endsWith(".js")) {
-          File dest = new File(destDir, file.getName());
-          Files.copy(file, dest);
+      File[] seFiles = seDir.listFiles();
+      if (seFiles != null) {
+        for (File file : seFiles) {
+          if (file.getName().endsWith(".js")) {
+            File dest = new File(destDir, file.getName());
+            Files.copy(file, dest);
+          }
         }
       }
 

java/client/test/org/openqa/selenium/javascript/TestFileLocator.java

@@ -48,11 +48,14 @@ public static List<File> findTestFiles() {
 
   private static List<File> findTestFiles(File directory, FilenameFilter filter) {
     List<File> files = Lists.newLinkedList();
-    for (File file : directory.listFiles()) {
-      if (file.isDirectory()) {
-        files.addAll(findTestFiles(file, filter));
-      } else if (filter.accept(file.getParentFile(), file.getName())) {
-        files.add(file);
+    File[] list = directory.listFiles();
+    if (list != null) {
+      for (File file : list) {
+        if (file.isDirectory()) {
+          files.addAll(findTestFiles(file, filter));
+        } else if (filter.accept(file.getParentFile(), file.getName())) {
+          files.add(file);
+        }
       }
     }
     return files;

java/server/src/org/openqa/selenium/remote/server/handler/UploadFile.java

@@ -42,7 +42,7 @@ public String call() throws Exception {
     new Zip().unzip(file, tempDir);
     // Select the first file
     File[] allFiles = tempDir.listFiles();
-    if (allFiles.length != 1) {
+    if (allFiles == null || allFiles.length != 1) {
       throw new WebDriverException("Expected there to be only 1 file. There were: " +
           allFiles.length);
     }