Read the fp-info-cache on pcb file load rather than on frame open

Otherwise in standalone mode pcbnew will never load the cache files and also later erase them :/

include/footprint_info.h

@@ -204,6 +204,14 @@ public:
         return m_list;
     }
 
+    /**
+     * @return Clears the footprint info cache
+     */
+    void Clear()
+    {
+        m_list.clear();
+    }
+
     /**
      * Get info for a footprint by id.
      */

pcbnew/files.cpp

@@ -54,6 +54,7 @@
 #include <plugins/cadstar/cadstar_pcb_archive_plugin.h>
 #include <plugins/eagle/eagle_plugin.h>
 #include <dialogs/dialog_imported_layers.h>
+#include "footprint_info_impl.h"
 
 
 //#define     USE_INSTRUMENTATION     1
@@ -608,6 +609,9 @@ bool PCB_EDIT_FRAME::OpenProjectFiles( const std::vector<wxString>& aFileSet, in
             Prj().SetReadOnly();
     }
 
+    // Clear the cache footprint list which may be project specific
+    GFootprintList.Clear();
+
     if( is_new )
     {
         // Link the existing blank board to the new project
@@ -677,6 +681,11 @@ bool PCB_EDIT_FRAME::OpenProjectFiles( const std::vector<wxString>& aFileSet, in
 
         SetBoard( loadedBoard );
 
+        if( GFootprintList.GetCount() == 0 )
+        {
+            GFootprintList.ReadCacheFromFile( Prj().GetProjectPath() + "fp-info-cache" );
+        }
+
         if( loadedBoard->m_LegacyDesignSettingsLoaded )
         {
             Prj().GetProjectFile().NetSettings().ResolveNetClassAssignments( true );

pcbnew/pcb_base_edit_frame.cpp

@@ -50,10 +50,6 @@ PCB_BASE_EDIT_FRAME::PCB_BASE_EDIT_FRAME( KIWAY* aKiway, wxWindow* aParent,
         m_selectionFilterPanel( nullptr ),
         m_appearancePanel( nullptr )
 {
-    if( !GFootprintList.GetCount() )
-    {
-        GFootprintList.ReadCacheFromFile( Prj().GetProjectPath() + "fp-info-cache" );
-    }
 }