NETLIST_EXPORTER_SPICE: add space to the not allowed chars in netnames

Not allowed chars are replaced by '_'
From master branch
Fixes #14724
https://gitlab.com/kicad/code/kicad/issues/14724

eeschema/netlist_exporters/netlist_exporter_spice.cpp

@@ -278,7 +278,7 @@ void NETLIST_EXPORTER_SPICE::ConvertToSpiceMarkup( std::string& aNetName )
 
     convertMarkup( root );
 
-    // Remove ngspice-disallowed chars
+    // Replace all ngspice-disallowed chars in netnames by a '_'
     std::replace( converted.begin(), converted.end(), '%', '_' );
     std::replace( converted.begin(), converted.end(), '(', '_' );
     std::replace( converted.begin(), converted.end(), ')', '_' );
@@ -288,6 +288,7 @@ void NETLIST_EXPORTER_SPICE::ConvertToSpiceMarkup( std::string& aNetName )
     std::replace( converted.begin(), converted.end(), '<', '_' );
     std::replace( converted.begin(), converted.end(), '>', '_' );
     std::replace( converted.begin(), converted.end(), '~', '_' );
+    std::replace( converted.begin(), converted.end(), ' ', '_' );
 
     aNetName = converted;
 }