Eeschema: avoid crashes when the tool highlight or delete is activated and clicking in a empty schematic.

Was a nullptr not tested.

eeschema/ee_collectors.cpp

@@ -104,7 +104,8 @@ void EE_COLLECTOR::Collect( EDA_ITEM* aItem, const KICAD_T aFilterList[], const
     // remember where the snapshot was taken from and pass refPos to the Inspect() function.
     SetRefPos( aPos );
 
-    if( aItem->Type() == LIB_PART_T )
+    // aItem can be null for empty schematics
+    if( aItem && aItem->Type() == LIB_PART_T )
         static_cast<LIB_PART*>( aItem )->Visit( m_inspector, nullptr, m_ScanTypes );
     else
         EDA_ITEM::IterateForward( aItem, m_inspector, nullptr, m_ScanTypes );

eeschema/tools/ee_picker_tool.h

@@ -74,7 +74,7 @@ public:
      */
     inline void SetClickHandler( CLICK_HANDLER aHandler )
     {
-        assert( !m_clickHandler );
+        wxASSERT( !m_clickHandler );
         m_clickHandler = aHandler;
     }
 
@@ -84,7 +84,7 @@ public:
      */
     inline void SetMotionHandler( MOTION_HANDLER aHandler )
     {
-        assert( !m_motionHandler );
+        wxASSERT( !m_motionHandler );
         m_motionHandler = aHandler;
     }
 
@@ -94,7 +94,7 @@ public:
      */
     inline void SetCancelHandler( CANCEL_HANDLER aHandler )
     {
-        assert( !m_cancelHandler );
+        wxASSERT( !m_cancelHandler );
         m_cancelHandler = aHandler;
     }
 
@@ -104,7 +104,7 @@ public:
      */
     inline void SetFinalizeHandler( FINALIZE_HANDLER aHandler )
     {
-        assert( !m_finalizeHandler );
+        wxASSERT( !m_finalizeHandler );
         m_finalizeHandler = aHandler;
     }
 

eeschema/tools/ee_selection_tool.cpp

@@ -764,6 +764,9 @@ static KICAD_T nodeTypes[] =
 
 EDA_ITEM* EE_SELECTION_TOOL::GetNode( VECTOR2I aPosition )
 {
+    if( m_frame->GetScreen()->GetDrawItems() == nullptr )   // Empty schematics
+        return nullptr;
+
     EE_COLLECTOR collector;
 
     int thresholdMax = KiROUND( getView()->ToWorld( HITTEST_THRESHOLD_PIXELS ) );