SCH_PIN: Guard the calculated map

Pins are used in threaded application so we need to keep the
precalculation map guarded

eeschema/sch_pin.cpp

@@ -67,6 +67,8 @@ wxString SCH_PIN::GetDefaultNetName( const SCH_SHEET_PATH aPath )
     if( m_pin->IsPowerConnection() )
         return m_pin->GetName();
 
+    std::lock_guard<std::mutex> lock( m_netmap_mutex );
+
     if( m_net_name_map.count( aPath ) > 0 )
         return m_net_name_map.at( aPath );
 

eeschema/sch_pin.h

@@ -26,6 +26,9 @@
 #include <sch_sheet_path.h>
 #include <lib_pin.h>
 
+#include <mutex>
+#include <map>
+
 class SCH_COMPONENT;
 
 class SCH_PIN : public SCH_ITEM
@@ -37,6 +40,7 @@ class SCH_PIN : public SCH_ITEM
     bool           m_isDangling;
 
     /// The name that this pin connection will drive onto a net
+    std::mutex m_netmap_mutex;
     std::map<const SCH_SHEET_PATH, wxString> m_net_name_map;
 
 public: