Fix bugs in Export to SVG.

We were trying to handle aOnlyOneFile at two different levels
which was preventing the Silk layer from going through the
right routine (and preventing board outlines from getting
drawn if selected).

We were also overwriting the references color local variable
before using it, meaning the reference was always rendered in
the value's color.

Fixes: lp:1774171
* https://bugs.launchpad.net/kicad/+bug/1774171

pcbnew/plot_brditems_plotter.cpp

@@ -210,43 +210,22 @@ void BRDITEMS_PLOTTER::PlotPad( D_PAD* aPad, COLOR4D aColor, EDA_DRAW_MODE_T aPl
 
 bool BRDITEMS_PLOTTER::PlotAllTextsModule( MODULE* aModule )
 {
-    // see if we want to plot VALUE and REF fields
-    bool trace_val = GetPlotValue();
-    bool trace_ref = GetPlotReference();
-
     TEXTE_MODULE* textModule = &aModule->Reference();
     LAYER_NUM     textLayer = textModule->GetLayer();
 
-    if( textLayer >= PCB_LAYER_ID_COUNT )       // how will this ever be true?
-        return false;
-
-    if( !m_layerMask[textLayer] )
-        trace_ref = false;
-
-    if( !textModule->IsVisible() && !GetPlotInvisibleText() )
-        trace_ref = false;
+    if( GetPlotReference() && m_layerMask[textLayer]
+        && ( textModule->IsVisible() || GetPlotInvisibleText() ) )
+    {
+        PlotTextModule( textModule, getColor( textLayer ) );
+    }
 
     textModule = &aModule->Value();
     textLayer = textModule->GetLayer();
 
-    if( textLayer > PCB_LAYER_ID_COUNT )        // how will this ever be true?
-        return false;
-
-    if( !m_layerMask[textLayer] )
-        trace_val = false;
-
-    if( !textModule->IsVisible() && !GetPlotInvisibleText() )
-        trace_val = false;
-
-    // Plot text fields, if allowed
-    if( trace_ref )
+    if( GetPlotValue() && m_layerMask[textLayer]
+        && ( textModule->IsVisible() || GetPlotInvisibleText() ) )
     {
-        PlotTextModule( &aModule->Reference(), getColor( textLayer ) );
-    }
-
-    if( trace_val )
-    {
-        PlotTextModule( &aModule->Value(), getColor( textLayer ) );
+        PlotTextModule( textModule, getColor( textLayer ) );
     }
 
     for( BOARD_ITEM* item = aModule->GraphicalItemsList().GetFirst(); item; item = item->Next() )