Detach in API destructor

library/DFHackAPI.cpp

@@ -187,6 +187,8 @@ API::API (const string path_to_xml)
 
 API::~API()
 {
+    // FIXME: call all finishread* methods here
+    Detach();
     delete d;
 }
 
@@ -1439,6 +1441,8 @@ bool API::Attach()
 
 bool API::Detach()
 {
+    if(!d->p)
+        return false;
     if (!d->p->detach())
     {
         return false;