Sonar Qube Key 'xx' belongs to a component which is not a Project - sonarqube

Question

SonarQube gets this error when trying to anaylze the pom.xml. I looked it up in the github repository of SQ and found nothing.
SonarQube version: 7.9.5
Java version: 1.8
[WARNING] Unable to analyse file 'pom.xml'.
java.lang.IllegalStateException: Key 'com.example:app' belongs to a component which is not a Project
at org.sonar.scanner.scan.filesystem.MetadataGenerator.setMetadata(MetadataGenerator.java:72)
at org.sonar.scanner.scan.filesystem.FileIndexer.lambda$indexFile$0(FileIndexer.java:134)
at org.sonar.api.batch.fs.internal.DefaultInputFile.checkMetadata(DefaultInputFile.java:91)
at org.sonar.api.batch.fs.internal.DefaultInputFile.charset(DefaultInputFile.java:230)
at org.sonar.api.batch.fs.internal.DefaultInputFile.contents(DefaultInputFile.java:115)
at org.sonarsource.analyzer.commons.xml.XmlFile.<init>(XmlFile.java:78)
at org.sonarsource.analyzer.commons.xml.XmlFile.create(XmlFile.java:89)
at org.sonar.plugins.java.XmlFileSensor.scanFile(XmlFileSensor.java:102)
at org.sonar.plugins.java.XmlFileSensor.execute(XmlFileSensor.java:86)
at org.sonar.scanner.sensor.AbstractSensorWrapper.analyse(AbstractSensorWrapper.java:48)
at org.sonar.scanner.sensor.ModuleSensorsExecutor.execute(ModuleSensorsExecutor.java:85)
at org.sonar.scanner.sensor.ModuleSensorsExecutor.lambda$execute$1(ModuleSensorsExecutor.java:59)
at org.sonar.scanner.sensor.ModuleSensorsExecutor.withModuleStrategy(ModuleSensorsExecutor.java:77)
at org.sonar.scanner.sensor.ModuleSensorsExecutor.execute(ModuleSensorsExecutor.java:59)
at org.sonar.scanner.scan.ModuleScanContainer.doAfterStart(ModuleScanContainer.java:82)
at org.sonar.core.platform.ComponentContainer.startComponents(ComponentContainer.java:136)
at org.sonar.core.platform.ComponentContainer.execute(ComponentContainer.java:122)
at org.sonar.scanner.scan.ProjectScanContainer.scan(ProjectScanContainer.java:400)
at org.sonar.scanner.scan.ProjectScanContainer.scanRecursively(ProjectScanContainer.java:395)
at org.sonar.scanner.scan.ProjectScanContainer.doAfterStart(ProjectScanContainer.java:358)
at org.sonar.core.platform.ComponentContainer.startComponents(ComponentContainer.java:136)
at org.sonar.core.platform.ComponentContainer.execute(ComponentContainer.java:122)
at org.sonar.scanner.bootstrap.GlobalContainer.doAfterStart(GlobalContainer.java:141)
at org.sonar.core.platform.ComponentContainer.startComponents(ComponentContainer.java:136)
at org.sonar.core.platform.ComponentContainer.execute(ComponentContainer.java:122)
at org.sonar.batch.bootstrapper.Batch.doExecute(Batch.java:73)
at org.sonar.batch.bootstrapper.Batch.execute(Batch.java:67)
at org.sonarsource.scanner.api.internal.batch.BatchIsolatedLauncher.execute(BatchIsolatedLauncher.java:46)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.sonarsource.scanner.api.internal.IsolatedLauncherProxy.invoke(IsolatedLauncherProxy.java:60)
at com.sun.proxy.$Proxy25.execute(Unknown Source)
at org.sonarsource.scanner.api.EmbeddedScanner.doExecute(EmbeddedScanner.java:189)
at org.sonarsource.scanner.api.EmbeddedScanner.execute(EmbeddedScanner.java:138)
at org.sonarsource.scanner.maven.bootstrap.ScannerBootstrapper.execute(ScannerBootstrapper.java:65)
at org.sonarsource.scanner.maven.SonarQubeMojo.execute(SonarQubeMojo.java:104)
at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:137)
at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:210)
at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:156)
at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:148)
at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:117)
at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:81)
at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build(SingleThreadedBuilder.java:56)
at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:128)
at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:305)
at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:192)
at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:105)
at org.apache.maven.cli.MavenCli.execute(MavenCli.java:957)
at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:289)
at org.apache.maven.cli.MavenCli.main(MavenCli.java:193)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:282)
at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:225)
at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:406)
at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:347)
Caused by: org.sonar.api.utils.MessageException: Key 'com.example:app' belongs to a component which is not a Project