A BOARD may not always have a project

For example, if it's the footprint editor model

Fixes https://gitlab.com/kicad/code/kicad/-/issues/15283


(cherry picked from commit 2459949d0d)

pcbnew/board.cpp

@@ -367,8 +367,11 @@ void BOARD::GetContextualTextVars( wxArrayString* aVars ) const
 
     GetTitleBlock().GetContextualTextVars( aVars );
 
-    for( std::pair<wxString, wxString> entry : GetProject()->GetTextVars() )
-        add( entry.first );
+    if( GetProject() )
+    {
+        for( std::pair<wxString, wxString> entry : GetProject()->GetTextVars() )
+            add( entry.first );
+    }
 }