cpp: Add safety checks for key update

* lang/cpp/src/key.cpp (Key::update): Check that the key is
not NULL.
* lang/cpp/src/verificationresult.cpp (GpgME::Signature::key):
Check for fingerprint.

1 files changed, 3 insertions, 0 deletions

diff --git a/lang/cpp/src/key.cpp b/lang/cpp/src/key.cpp
index 61b3eb77..8fc266ff 100644
--- a/lang/cpp/src/key.cpp
+++ b/lang/cpp/src/key.cpp
@@ -347,6 +347,9 @@ const Key &Key::mergeWith(const Key &other)
 
 void Key::update()
 {
+    if (isNull() || !primaryFingerprint()) {
+        return;
+    }
     auto ctx = Context::createForProtocol(protocol());
     if (!ctx) {
         return;