Fix md5_check.py crashing when adding a new zip file

build/android/gyp/util/md5_check.py

Index: build/android/gyp/util/md5_check.py
diff --git a/build/android/gyp/util/md5_check.py b/build/android/gyp/util/md5_check.py
index 2ddc3ac48a18f1e4c3e9f11178f6d88da1461709..a68bdc9d3699990d86d0519a642055e74b3ee0a3 100644
--- a/build/android/gyp/util/md5_check.py
+++ b/build/android/gyp/util/md5_check.py
@@ -340,9 +340,12 @@ class _Metadata(object):
   def IterSubpaths(self, path):
     """Returns a generator for all subpaths in the given zip.
 
-    If the given path is not a zip file, returns an empty generator.
+    If the given path is not a zip file or doesn't exist, returns an empty
+    iterable.
     """
     outer_entry = self._GetEntry(path)
+    if not outer_entry:
+      return ()
     subentries = outer_entry.get('entries', [])
     return (entry['path'] for entry in subentries)