From 8e78d8de53fc586d82efcb0975f264fbc7f049e4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ana=20Mar=C3=ADa=20Mart=C3=ADnez=20G=C3=B3mez?=
 <anamaria.martinezgom@FireEye.com>
Date: Tue, 30 Jun 2020 14:21:39 +0200
Subject: [PATCH] Fix KeyError when deleting nonexistent keys

`hidden_meta` saves not only the existing hidden meta keys, but also
those who don't exist with value `None`. For example:
```
{'capa/path': None, 'capa/nursery': None}
```

Deleting nonexistent keys raises a `KeyError` exception.
---
 capa/rules.py | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/capa/rules.py b/capa/rules.py
index d60c17c9..ae27dd4d 100644
--- a/capa/rules.py
+++ b/capa/rules.py
@@ -590,10 +590,11 @@ class Rule(object):
         # save off the existing hidden meta values,
         # emit the document,
         # and re-add the hidden meta.
-        hidden_meta = {
-            key: meta.get(key)
-            for key in HIDDEN_META_KEYS
-        }
+        hidden_meta = {}
+        for key in HIDDEN_META_KEYS:
+            value = meta.get(key)
+            if value:
+                hidden_meta[key] = value
 
         for key in hidden_meta.keys():
             del meta[key]