Accept empty "(fp)" statements.

Fixes https://gitlab.com/kicad/code/kicad/-/issues/20002

common/dsnlexer.cpp

@@ -333,6 +333,12 @@ bool DSNLEXER::IsSymbol( int aTok )
 }
 
 
+bool DSNLEXER::IsNumber( int aTok )
+{
+    return aTok == DSN_NUMBER;
+}
+
+
 void DSNLEXER::Expecting( int aTok ) const
 {
     wxString errText = wxString::Format( _( "Expecting %s" ), GetTokenString( aTok ) );
@@ -410,7 +416,7 @@ int DSNLEXER::NeedSYMBOLorNUMBER()
 {
     int  tok = NextTok();
 
-    if( !IsSymbol( tok ) && tok!=DSN_NUMBER )
+    if( !IsSymbol( tok ) && !IsNumber( tok ) )
         Expecting( "a symbol or number" );
 
     return tok;
@@ -421,7 +427,7 @@ int DSNLEXER::NeedNUMBER( const char* aExpectation )
 {
     int tok = NextTok();
 
-    if( tok != DSN_NUMBER )
+    if( !IsNumber( tok ) )
     {
         wxString errText = wxString::Format( _( "need a number for '%s'" ),
                                              wxString::FromUTF8( aExpectation ).GetData() );

include/dsnlexer.h

@@ -332,6 +332,8 @@ public:
      */
     static bool IsSymbol( int aTok );
 
+    static bool IsNumber( int aTok );
+
     /**
      * Throw an #IO_ERROR exception with an input file specific error message.
      *

pcbnew/netlist_reader/kicad_netlist_reader.cpp

@@ -743,7 +743,15 @@ void KICAD_NETLIST_PARSER::parseLibPartList()
                 if( token != T_fp )
                     Expecting( T_fp );
 
-                NeedSYMBOLorNUMBER();
+                token = NextTok();
+
+                // Accept an empty (fp) sexpr.  We do write them out.
+                if( token == T_RIGHT )
+                    continue;
+
+                if( !IsSymbol( token ) && !IsNumber( token ) )
+                   Expecting( "footprint ID" );
+
                 footprintFilters.Add( From_UTF8( CurText() ) );
                 NeedRIGHT();
             }