Add support for multiple asset dirs (-A)

Bug: 12608034
Change-Id: I02c5a1a73b83498d799570428cca3dd914f8ac11
diff --git a/tools/aapt/Command.cpp b/tools/aapt/Command.cpp
index 632efe0..40845e3 100644
--- a/tools/aapt/Command.cpp
+++ b/tools/aapt/Command.cpp
@@ -1896,7 +1896,7 @@
 
     N = bundle->getFileSpecCount();
     if (N < 1 && bundle->getResourceSourceDirs().size() == 0 && bundle->getJarFiles().size() == 0
-            && bundle->getAndroidManifestFile() == NULL && bundle->getAssetSourceDir() == NULL) {
+            && bundle->getAndroidManifestFile() == NULL && bundle->getAssetSourceDirs().size() == 0) {
         fprintf(stderr, "ERROR: no input files\n");
         goto bail;
     }