Don't assume we have a MODULE parent

Fixes https://gitlab.com/kicad/code/kicad/-/issues/6063

pcbnew/class_pad.cpp

@@ -1233,6 +1233,12 @@ const BOX2I D_PAD::ViewBBox() const
 }
 
 
+MODULE* D_PAD::GetParent() const
+{
+    return dynamic_cast<MODULE*>( m_Parent );
+}
+
+
 void D_PAD::ImportSettingsFrom( const D_PAD& aMasterPad )
 {
     SetShape( aMasterPad.GetShape() );

pcbnew/class_pad.h

@@ -108,7 +108,7 @@ public:
         return false;
     }
 
-    MODULE* GetParent() const { return (MODULE*) m_Parent; }
+    MODULE* GetParent() const;
 
     /**
      * Imports the pad settings from aMasterPad.