IllegalArgumentException in diagram synthesis

[petervdonovan]

An exception occurred during diagram synthesis\
java.lang.IllegalArgumentException\
    at org.lflang.ast.ASTUtils.toTimeValue(ASTUtils.java:681)\
    at org.lflang.ast.ASTUtils.getLiteralTimeValue(ASTUtils.java:1151)\
    at org.lflang.generator.ReactorInstance.getTimeValue(ReactorInstance.java:717)\
    at org.lflang.generator.ActionInstance.<init>(ActionInstance.java:69)\
    at org.lflang.generator.ReactorInstance.<init>(ReactorInstance.java:885)\
    at org.lflang.generator.ReactorInstance.<init>(ReactorInstance.java:874)\
    at org.lflang.generator.ReactorInstance.<init>(ReactorInstance.java:105)\
    at org.lflang.diagram.synthesis.LinguaFrancaSynthesis.transform(LinguaFrancaSynthesis.java:315)\
    at org.lflang.diagram.synthesis.LinguaFrancaSynthesis.transform(LinguaFrancaSynthesis.java:141)\
    at de.cau.cs.kieler.klighd.syntheses.AbstractDiagramSynthesis.transform(AbstractDiagramSynthesis.java:220)\
    at de.cau.cs.kieler.klighd.syntheses.ReinitializingDiagramSynthesisProxy.transform(ReinitializingDiagramSynthesisProxy.java:289)\
    at de.cau.cs.kieler.klighd.ViewContext.update(ViewContext.java:454)\
    at de.cau.cs.kieler.klighd.ViewContext.update(ViewContext.java:389)\
    at de.cau.cs.kieler.klighd.ViewContext.update(ViewContext.java:346)\
    at de.cau.cs.kieler.klighd.lsp.KGraphDiagramUpdater.lambda$6(KGraphDiagramUpdater.java:267)\
    at de.cau.cs.kieler.klighd.lsp.launch.AbstractLanguageServer.lambda$1(AbstractLanguageServer.java:117)\
    at de.cau.cs.kieler.klighd.lsp.launch.AbstractLanguageServer.configureAndRun(AbstractLanguageServer.java:96)\
    at org.lflang.diagram.lsp.LanguageDiagramServer.start(LanguageDiagramServer.java:111)\
    at org.lflang.diagram.lsp.LanguageDiagramServer.main(LanguageDiagramServer.java:107)\

This error appears as an error message that pops up in the bottom-left corner of the window.

This issue is encountered while interacting with the diagram for the C version of LoopDistributedCentralized using a recent version of the VS Code extension (more recent than the latest release). I think that this happened while I was editing time values appearing in the file, so it is unsurprising that this error should occur; however, we should more gracefully handle cases when the model is temporarily invalid.