Fixes a bug: currency converter never shows error message for service failures (#1799)

* check status before registering callback

* optimize the style for error msg

src/CalcViewModel/DataLoaders/CurrencyDataLoader.cpp

@@ -188,10 +188,9 @@ void CurrencyDataLoader::ResetLoadStatus()
 #pragma optimize("", off) // Turn off optimizations to work around DevDiv 393321
 void CurrencyDataLoader::LoadData()
 {
-    RegisterForNetworkBehaviorChanges();
-
     if (!LoadFinished())
     {
+        RegisterForNetworkBehaviorChanges();
         create_task([this]() -> task<bool> {
             vector<function<future<bool>()>> loadFunctions = {
                 [this]() { return TryLoadDataFromCacheAsync(); },

src/Calculator/Views/UnitConverter.xaml

@@ -673,9 +673,8 @@
                                 </ResourceDictionary>
                             </HyperlinkButton.Resources>
                         </HyperlinkButton>
-                        <TextBlock Margin="3,7,0,0" Style="{ThemeResource CaptionTextBlockStyle}">
+                        <TextBlock Margin="3,6,0,0" Style="{ThemeResource CaptionTextBlockStyle}">
                             <Run x:Name="CurrencySecondaryStatus"
-                                 FontWeight="SemiBold"
                                  Text=""/>
                         </TextBlock>
                     </StackPanel>