Free memory in dxf import sooner on bad_alloc

(cherry picked from commit b18e441a88)

pcbnew/import_gfx/dxf_import_plugin.cpp

@@ -124,6 +124,12 @@ bool DXF_IMPORT_PLUGIN::Load( const wxString& aFileName )
     }
     catch( const std::bad_alloc& )
     {
+        m_layers.clear();
+        m_blocks.clear();
+        m_styles.clear();
+
+        m_internalImporter.ClearShapes();
+
         reportMsg( _( "Memory was exhausted trying to load the DXF, it may be too large." ) );
         return false;
     }

pcbnew/import_gfx/graphics_importer.h

@@ -189,6 +189,14 @@ public:
         return m_items;
     }
 
+    /**
+     * Empties out the imported shapes list
+     */
+    void ClearItems()
+    {
+        m_items.clear();
+    }
+
     ///< Default line thickness (in mm)
     static constexpr unsigned int DEFAULT_LINE_WIDTH_DFX = 1;
 

pcbnew/import_gfx/graphics_importer_buffer.h

@@ -354,6 +354,11 @@ public:
         return m_shapes;
     }
 
+    void ClearShapes()
+    {
+        m_shapes.clear();
+    }
+
     void PostprocessNestedPolygons();
 
 protected: