Icon-related NPE with IntelliJ 2023.3.2

[hho]

When opening a project with the plugin active, I get the following exception:

Unhandled exception in [CoroutineName(com.intellij.ui.IconCalculatingService), StandaloneCoroutine{Cancelling}@60a6a3af, Dispatchers.Default]

java.lang.NullPointerException: Cannot invoke "javax.imageio.metadata.IIOMetadata.getAsTree(String)" because the return value of "javax.imageio.ImageReader.getImageMetadata(int)" is null
	at de.docs_as_co.intellij.plugin.drawio.DiagramsFileUtil$Companion.isDiagramsFile(DiagramsFileUtil.kt:70)
	at de.docs_as_co.intellij.plugin.drawio.icons.DiagramsEditorIconProvider.getIcon(DiagramsEditorIconProvider.kt:15)
	at com.intellij.util.PsiIconUtil.getProvidersIcon(PsiIconUtil.kt:20)
	at com.intellij.psi.impl.ElementBase.doComputeIconNow(ElementBase.java:98)
	at com.intellij.psi.impl.ElementBase.lambda$computeIconNow$3(ElementBase.java:94)
	at com.intellij.util.AstLoadingFilter.disallowTreeLoading(AstLoadingFilter.java:129)
	at com.intellij.util.AstLoadingFilter.disallowTreeLoading(AstLoadingFilter.java:118)
	at com.intellij.psi.impl.ElementBase.computeIconNow(ElementBase.java:94)
	at com.intellij.psi.impl.ElementBase.lambda$static$0(ElementBase.java:45)
	at com.intellij.ui.DeferredIconImpl.evaluate(DeferredIconImpl.kt:290)
	at com.intellij.ui.DeferredIconImpl$scheduleCalculationIfNeeded$1$result$1$1.invoke(DeferredIconImpl.kt:226)
	at com.intellij.ui.DeferredIconImpl$scheduleCalculationIfNeeded$1$result$1$1.invoke(DeferredIconImpl.kt:226)
	at com.intellij.openapi.application.rw.InternalReadAction.insideReadAction(InternalReadAction.kt:108)
	at com.intellij.openapi.application.rw.InternalReadAction.access$insideReadAction(InternalReadAction.kt:16)
	at com.intellij.openapi.application.rw.InternalReadAction$tryReadCancellable$2.invoke(InternalReadAction.kt:95)
	at com.intellij.openapi.application.rw.InternalReadAction$tryReadCancellable$2.invoke(InternalReadAction.kt:94)
	at com.intellij.openapi.application.rw.CancellableReadActionKt$cancellableReadActionInternal$1.invoke$lambda$1$lambda$0(cancellableReadAction.kt:38)
	at com.intellij.openapi.application.impl.ApplicationImpl.tryRunReadAction(ApplicationImpl.java:1075)
	at com.intellij.openapi.application.rw.CancellableReadActionKt$cancellableReadActionInternal$1.invoke$lambda$1(cancellableReadAction.kt:36)
	at com.intellij.openapi.progress.util.ProgressIndicatorUtilService.runActionAndCancelBeforeWrite(ProgressIndicatorUtilService.java:73)
	at com.intellij.openapi.progress.util.ProgressIndicatorUtils.runActionAndCancelBeforeWrite(ProgressIndicatorUtils.java:128)
	at com.intellij.openapi.application.rw.CancellableReadActionKt$cancellableReadActionInternal$1.invoke(cancellableReadAction.kt:34)
	at com.intellij.openapi.progress.CoroutinesKt.blockingContextInner(coroutines.kt:321)
	at com.intellij.openapi.progress.CoroutinesKt.blockingContext(coroutines.kt:310)
	at com.intellij.openapi.application.rw.CancellableReadActionKt.cancellableReadActionInternal(cancellableReadAction.kt:31)
	at com.intellij.openapi.application.rw.InternalReadAction.tryReadCancellable(InternalReadAction.kt:94)
	at com.intellij.openapi.application.rw.InternalReadAction.tryReadAction(InternalReadAction.kt:78)
	at com.intellij.openapi.application.rw.InternalReadAction.readLoop(InternalReadAction.kt:65)
	at com.intellij.openapi.application.rw.InternalReadAction.access$readLoop(InternalReadAction.kt:16)
	at com.intellij.openapi.application.rw.InternalReadAction$runReadAction$4.invokeSuspend(InternalReadAction.kt:44)
	at com.intellij.openapi.application.rw.InternalReadAction$runReadAction$4.invoke(InternalReadAction.kt)
	at com.intellij.openapi.application.rw.InternalReadAction$runReadAction$4.invoke(InternalReadAction.kt)
	at kotlinx.coroutines.intrinsics.UndispatchedKt.startUndispatchedOrReturn(Undispatched.kt:78)
	at kotlinx.coroutines.BuildersKt__Builders_commonKt.withContext(Builders.common.kt:167)
	at kotlinx.coroutines.BuildersKt.withContext(Unknown Source)
	at com.intellij.openapi.application.rw.InternalReadAction.runReadAction(InternalReadAction.kt:40)
	at com.intellij.openapi.application.rw.PlatformReadWriteActionSupport.executeReadAction(PlatformReadWriteActionSupport.kt:38)
	at com.intellij.openapi.application.ReadWriteActionSupport.executeReadAction$default(ReadWriteActionSupport.kt:15)
	at com.intellij.openapi.application.CoroutinesKt.constrainedReadAction(coroutines.kt:58)
	at com.intellij.openapi.application.CoroutinesKt.readAction(coroutines.kt:25)
	at com.intellij.ui.DeferredIconImpl$scheduleCalculationIfNeeded$1$invokeSuspend$$inlined$evaluateDeferred$1.invokeSuspend(IconDeferrerImpl.kt:109)
	at com.intellij.ui.DeferredIconImpl$scheduleCalculationIfNeeded$1$invokeSuspend$$inlined$evaluateDeferred$1.invoke(IconDeferrerImpl.kt)
	at com.intellij.ui.DeferredIconImpl$scheduleCalculationIfNeeded$1$invokeSuspend$$inlined$evaluateDeferred$1.invoke(IconDeferrerImpl.kt)
	at kotlinx.coroutines.intrinsics.UndispatchedKt.startUndispatchedOrReturn(Undispatched.kt:78)
	at kotlinx.coroutines.BuildersKt__Builders_commonKt.withContext(Builders.common.kt:167)
	at kotlinx.coroutines.BuildersKt.withContext(Unknown Source)
	at com.intellij.ui.DeferredIconImpl$scheduleCalculationIfNeeded$1.invokeSuspend(DeferredIconImpl.kt:386)
	at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)
	at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:108)
	at kotlinx.coroutines.scheduling.CoroutineScheduler.runSafely(CoroutineScheduler.kt:584)
	at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.executeTask(CoroutineScheduler.kt:793)
	at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.runWorker(CoroutineScheduler.kt:697)
	at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.run(CoroutineScheduler.kt:684)
	Suppressed: kotlinx.coroutines.internal.DiagnosticCoroutineContextException: [CoroutineName(com.intellij.ui.IconCalculatingService), StandaloneCoroutine{Cancelled}@60a6a3af, Dispatchers.Default]