Failure to read XML files that lack `lat` or `lon` values for some nodes

[sebkur]

When converting a PBF history file to XML using osmium, the XML will contain nodes that don't have any lon or lat attributes. Attempting to parse such XML files:

Exception in thread "main" java.lang.RuntimeException: error while processing input
        at de.topobyte.osm4j.xml.dynsax.OsmXmlIterator.hasNext(OsmXmlIterator.java:138)
        at de.topobyte.osm4j.utils.executables.OsmCount.run(OsmCount.java:59)
        at de.topobyte.osm4j.utils.executables.OsmCount.main(OsmCount.java:46)
Caused by: de.topobyte.osm4j.core.access.OsmInputException: error while parsing xml data
        at de.topobyte.osm4j.xml.dynsax.OsmXmlReader.read(OsmXmlReader.java:90)
        at de.topobyte.osm4j.xml.dynsax.OsmXmlIterator$1.run(OsmXmlIterator.java:94)
        at java.base/java.lang.Thread.run(Thread.java:829)
Caused by: java.lang.NullPointerException
        at java.base/jdk.internal.math.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:1838)
        at java.base/jdk.internal.math.FloatingDecimal.parseDouble(FloatingDecimal.java:110)
        at java.base/java.lang.Double.parseDouble(Double.java:543)
        at de.topobyte.osm4j.xml.dynsax.OsmSaxHandler.emit(OsmSaxHandler.java:283)
        at de.topobyte.xml.dynsax.DynamicSaxHandler.endElement(DynamicSaxHandler.java:127)
        at java.xml/com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.endElement(AbstractSAXParser.java:610)
        at java.xml/com.sun.org.apache.xerces.internal.parsers.AbstractXMLDocumentParser.emptyElement(AbstractXMLDocumentParser.java:184)
        at java.xml/com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanStartElement(XMLDocumentFragmentScannerImpl.java:1377)
        at java.xml/com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDriver.next(XMLDocumentFragmentScannerImpl.java:2710)
        at java.xml/com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImpl.java:605)
        at java.xml/com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:534)
        at java.xml/com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:888)
        at java.xml/com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:824)
        at java.xml/com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:141)
        at java.xml/com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(AbstractSAXParser.java:1216)
        at java.xml/com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(SAXParserImpl.java:635)
        at java.xml/com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl.parse(SAXParserImpl.java:324)
        at java.xml/javax.xml.parsers.SAXParser.parse(SAXParser.java:197)
        at de.topobyte.osm4j.xml.dynsax.OsmXmlReader.read(OsmXmlReader.java:88)