return better error message when ZipEntry has no data (it was closed before the data was retrieved)

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1894831 13f79535-47bb-0310-9956-ffa450edef68

poi-ooxml/src/main/java/org/apache/poi/openxml4j/util/ZipArchiveFakeEntry.java

@@ -88,8 +88,10 @@ import org.apache.poi.util.TempFile;
             } catch (FileNotFoundException e) {
                 throw new RuntimeException("temp file " + tempFile.getAbsolutePath() + " is missing");
             }
-        } else {
+        } else if (data != null) {
             return new UnsynchronizedByteArrayInputStream(data);
+        } else {
+            throw new RuntimeException("Cannot retrieve data from Zip Entry, probably because the Zip Entry was closed before the data was requested.");
         }
     }