Tried to open a text file with ER Modeler and got this in Error log

org.xml.sax.SAXParseException: Content is not allowed in prolog.
 at com.sun.org.apache.xerces.internal.util.ErrorHandlerWrapper.createSAXParseException(ErrorHandlerWrapper.java:195)
 at com.sun.org.apache.xerces.internal.util.ErrorHandlerWrapper.fatalError(ErrorHandlerWrapper.java:174)
 at com.sun.org.apache.xerces.internal.impl.XMLErrorReporter.reportError(XMLErrorReporter.java:388)
 at com.sun.org.apache.xerces.internal.impl.XMLScanner.reportFatalError(XMLScanner.java:1411)
 at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl$PrologDriver.next(XMLDocumentScannerImpl.java:1024)
 at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImpl.java:647)
 at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.next(XMLNSDocumentScannerImpl.java:140)
 at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:508)
 at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:807)
 at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:737)
 at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:107)
 at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(AbstractSAXParser.java:1205)
 at nmfl.axJ.a(Unknown Source)
 at nmfl.atg.b(Unknown Source)
 at nmfl.atg.d(Unknown Source)
 at nmfl.anB.a(Unknown Source)
 at nmfl.ajO.e(Unknown Source)
 at nmfl.atg.b(Unknown Source)
 at com.aquafold.datastudio.mainframe.i.actionPerformed(Unknown Source)
 at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1995)
 at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2318)
 at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:387)
 at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:242)
 at javax.swing.AbstractButton.doClick(AbstractButton.java:357)
 at com.jidesoft.plaf.vsnet.VsnetMenuItemUI.doClick(Unknown Source)
 at com.jidesoft.plaf.vsnet.VsnetMenuItemUI$MouseInputHandler.mouseReleased(Unknown Source)
 at java.awt.Component.processMouseEvent(Component.java:6041)
 at javax.swing.JComponent.processMouseEvent(JComponent.java:3265)
 at java.awt.Component.processEvent(Component.java:5806)
 at java.awt.Container.processEvent(Container.java:2058)
 at java.awt.Component.dispatchEventImpl(Component.java:4413)
 at java.awt.Container.dispatchEventImpl(Container.java:2116)
 at java.awt.Component.dispatchEvent(Component.java:4243)
 at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4322)
 at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3986)
 at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3916)
 at java.awt.Container.dispatchEventImpl(Container.java:2102)
 at java.awt.Window.dispatchEventImpl(Window.java:2440)
 at java.awt.Component.dispatchEvent(Component.java:4243)
 at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
 at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:273)
 at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:183)
 at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:173)
 at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:168)
 at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:160)
 at java.awt.EventDispatchThread.run(EventDispatchThread.java:121)