updater: Check the return value from ApplyImagePatch / ApplyBSDiffPatch

Return NULL to abort the update process. Note that returning ""
won't stop the script.

Change-Id: Ifd108c1356f7c92a905c8776247a8842c6445319
diff --git a/recovery.cpp b/recovery.cpp
index 1d22b24..6deeaaa 100644
--- a/recovery.cpp
+++ b/recovery.cpp
@@ -1107,6 +1107,7 @@
         }
         if (status != INSTALL_SUCCESS) {
             ui->Print("Installation aborted.\n");
+            ui->Print("OTA failed! Please power off the device to keep it in this state and file a bug report!\n");
 
             // If this is an eng or userdebug build, then automatically
             // turn the text display on if the script fails so the error