Added null condition check for mimetype

Change-Id: Ibddc9fec4618fd59c438a9f76df83aadae44f6d6
diff --git a/src/com/android/browser/DownloadSettings.java b/src/com/android/browser/DownloadSettings.java
index d9534e2..4ae00e3 100644
--- a/src/com/android/browser/DownloadSettings.java
+++ b/src/com/android/browser/DownloadSettings.java
@@ -136,7 +136,7 @@
         }
 
         //Add special check for .apk files with octet-stream mimetype
-        if (mimetype.equals(OCTET_STREAM) && filenameExtension.equals(APK_TYPE)) {
+        if (filenameExtension.equals(APK_TYPE) && mimetype != null && mimetype.equals(OCTET_STREAM)) {
             mimetype =  "application/vnd.android.package-archive";
         }