xmerge: ensure that the stream is cleaned up before the method returns

Change-Id: I377ae1a7b71c207313ad3468a51b1ab06b9fffd5
Reviewed-on: https://gerrit.libreoffice.org/11939
Reviewed-by: Noel Grandin <noelgrandin@gmail.com>
Tested-by: Noel Grandin <noelgrandin@gmail.com>

xmerge/source/xmerge/java/org/openoffice/xmerge/converter/xml/xslt/PluginFactoryImpl.java

@@ -147,6 +147,13 @@ public final class PluginFactoryImpl extends PluginFactory
         } catch (Exception e) {
 
         // It is okay for the property file to not exist.
+        } finally {
+            try {
+                if (is != null) {
+                    is.close();
+                }
+            } catch (IOException ex) {
+            }
         }
         return ext;
     }