santa-driver: Only try to use/release proc_t if proc_find found it.

Fix application deadlock.

Source/SantaGUI/SNTAppDelegate.m

@@ -71,7 +71,7 @@
 #pragma mark Connection handling
 
 - (void)createConnection {
-  dispatch_sync(dispatch_get_main_queue(), ^{
+  dispatch_async(dispatch_get_main_queue(), ^{
     __weak __typeof(self) weakSelf = self;
 
     self.listener = [[SNTXPCConnection alloc] initClientWithName:[SNTXPCNotifierInterface serviceId]

Source/santa-driver/SantaDecisionManager.cc

@@ -116,8 +116,11 @@ void SantaDecisionManager::DisconnectClient(bool itDied) {
 
 bool SantaDecisionManager::ClientConnected() {
   proc_t p = proc_find(client_pid_);
-  bool is_exiting = proc_exiting(p);
-  proc_rele(p);
+  bool is_exiting = false;
+  if (p) {
+    is_exiting = proc_exiting(p);
+    proc_rele(p);
+  }
   return (client_pid_ > 0 && !is_exiting);
 }