Move default format inside SPICE_VALUE_FORMAT

This ensures that the default format is the same, however the measurements are added

eeschema/sim/simulator_frame_ui.cpp

@@ -1521,7 +1521,6 @@ void SIMULATOR_FRAME_UI::AddMeasurement( const wxString& aCmd )
     }
 
     m_measurementsGrid->SetCellValue( row, COL_MEASUREMENT, aCmd );
-    SetMeasureFormat( row, { 3, wxS( "~V" ) } );
 
     UpdateMeasurement( row );
     updateMeasurementsFromGrid();

eeschema/sim/spice_value.cpp

@@ -40,10 +40,18 @@
 
 void SPICE_VALUE_FORMAT::FromString( const wxString& aString )
 {
-    long val;
-    aString.Left( 1 ).ToLong( &val );
-    Precision = (int) val;
-    Range = aString.Right( aString.Length() - 1 );
+    if( aString.IsEmpty() )
+    {
+        Precision = 3;
+        Range = wxS( "~V" );
+    }
+    else
+    {
+        long val;
+        aString.Left( 1 ).ToLong( &val );
+        Precision = (int) val;
+        Range = aString.Right( aString.Length() - 1 );
+    }
 }