Fp chooser: fix filter by pin count (incorrect count) with multi unit part

Previously, the pin count was the unit pin count, that is incorrect to select
a footprint. the symbol pin count is now used.

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

eeschema/fields_grid_table.cpp

@@ -72,10 +72,18 @@ static wxString netList( SCH_SYMBOL* aSymbol, SCH_SHEET_PATH& aSheetPath )
      */
     wxString netlist;
 
+    // We need the list of pins of the lib symbol, not just the pins of the current
+    // sch symbol, that can be just an unit of a multi-unit symbol, to be able to
+    // select/filter right footprints
     wxArrayString pins;
 
-    for( SCH_PIN* pin : aSymbol->GetPins( &aSheetPath ) )
-        pins.push_back( pin->GetNumber() + ' ' + pin->GetShownName() );
+    const std::unique_ptr< LIB_SYMBOL >& lib_symbol = aSymbol->GetLibSymbolRef();
+
+    if( lib_symbol )
+    {
+        for( SCH_PIN* pin : lib_symbol->GetPins( 0 /* all units */, 1 /* single bodyStyle */ ) )
+            pins.push_back( pin->GetNumber() + ' ' + pin->GetShownName() );
+    }
 
     if( !pins.IsEmpty() )
         netlist << EscapeString( wxJoin( pins, '\t' ), CTX_LINE );