Boards manager: when upgrading, first remove, then install

Author: Federico Fissore

app/src/cc/arduino/contributions/packages/ui/ContributionManagerUI.java

@@ -161,10 +161,10 @@ public void onInstallPressed(final ContributedPlatform platformToInstall, final
       List<String> errors = new LinkedList<>();
       try {
         setProgressVisible(true, tr("Installing..."));
-        errors.addAll(installer.install(platformToInstall, this::setProgress));
         if (platformToRemove != null && !platformToRemove.isReadOnly()) {
           errors.addAll(installer.remove(platformToRemove));
         }
+        errors.addAll(installer.install(platformToInstall, this::setProgress));
         onIndexesUpdated();
       } catch (Exception e) {
         throw new RuntimeException(e);