Gallery Picker: When uploading PNG file with extension JPG picture is shown in the picker but is not correct imported.

If i upload a PNG file with extension JPG the GalleryPicker uploads it and throws exception with message (Invalid resource).

The picker shows the picture with wrong size and let me add it in documents.

Document could not be published because of:

Caused by: javax.jcr.PathNotFoundException: vlc-media-player.jpg/hippogallery:original
[INFO] [talledLocalContainer] at org.apache.jackrabbit.core.NodeImpl$8.perform(NodeImpl.java:2163)
[INFO] [talledLocalContainer] at org.apache.jackrabbit.core.NodeImpl$8.perform(NodeImpl.java:2157)
[INFO] [talledLocalContainer] at org.apache.jackrabbit.core.session.SessionState.perform(SessionState.java:216)
[INFO] [talledLocalContainer] at org.apache.jackrabbit.core.ItemImpl.perform(ItemImpl.java:91)
[INFO] [talledLocalContainer] at org.apache.jackrabbit.core.NodeImpl.getNode(NodeImpl.java:2157)
[INFO] [talledLocalContainer] at org.hippoecm.repository.decorating.NodeDecorator.getNode(NodeDecorator.java:226)
[INFO] [talledLocalContainer] at de.netpioneer.heise.download.hippo.cms.repository.image.ImageNodeHandler.exportImage(ImageNodeHandler.java:127)
[INFO] [talledLocalContainer] at de.netpioneer.heise.download.hippo.cms.repository.image.ImageNodeHandler.exportImageForHandle(ImageNodeHandler.java:89)
[INFO] [talledLocalContainer] at de.netpioneer.heise.download.hippo.cms.convert.ImageLinkNodeConverter.getImageRefFromNode(ImageLinkNodeConverter.java:29)
[INFO] [talledLocalContainer] at de.netpioneer.heise.download.hippo.cms.convert.ImageNodeConverter.getImageRef(ImageNodeConverter.java:29)
[INFO] [talledLocalContainer] at de.netpioneer.heise.download.hippo.cms.convert.ImageNodeConverter.getHeiseImageContentFromNode(ImageNodeConverter.java:21)
[INFO] [talledLocalContainer] at de.netpioneer.heise.download.hippo.cms.convert.ThemenspecialConverter.convert(ThemenspecialConverter.java:70)
[INFO] [talledLocalContainer] at de.netpioneer.heise.download.hippo.cms.convert.ThemenspecialConverter.convert(ThemenspecialConverter.java:17)
[INFO] [talledLocalContainer] at de.netpioneer.heise.download.hippo.cms.export.ThemenspecialExporter.export(ThemenspecialExporter.java:33)
[INFO] [talledLocalContainer] ... 22 more
[INFO] [talledLocalContainer] at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
[INFO] [talledLocalContainer] at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
[INFO] [talledLocalContainer] at java.lang.Thread.run(Thread.java:745)
[INFO] [talledLocalContainer]