Make texstudio behave better when removing/upgrading from older versions

NB no version bump to the package needed here; where there are machines
that succesfully have the package installed already we don't want to
force a no-op "upgrade" upon them

packages/texstudio.xml

@@ -11,9 +11,24 @@
     <upgrade include='remove' />
     <upgrade include='install' />
 
+    <!-- tidy up legacy versions that use unins000.exe -->
+    <remove cmd='"%PROGRAMFILES(x86)%\TeXstudio\unins000.exe" /SP- /VERYSILENT /SUPPRESSMSGBOXES'>
+      <condition>
+        <check type="file" condition="exists" path="%PROGRAMFILES(x86)%\TeXstudio\unins000.exe" />
+      </condition>
+    </remove>
+
+    <!-- uninstaller for the "current" version. We acknowledge the possibility of two brief
+         unnecessary waitforprocess.cmds for the sake of not littering the entire xml
+         with repeated <condition>s -->
     <remove cmd='%WPKGSOFTWARE%\wpkg\tools\waitforprocess.cmd Un_A.exe' />
-    <remove cmd='"%PROGRAMFILES(x86)%\TeXstudio\uninstall.exe" /S' />
+    <remove cmd='"%PROGRAMFILES(x86)%\TeXstudio\uninstall.exe" /S'>
+      <condition>
+        <check type="file" condition="exists" path="%PROGRAMFILES(x86)%\TeXstudio\uninstall.exe" />
+      </condition>
+    </remove>
     <remove cmd='%WPKGSOFTWARE%\wpkg\tools\waitforprocess.cmd Un_A.exe' />
+
   </package>
 
 </packages:packages>