IconServlet.java is calling sendError() after getOutputStream() causing an exception

[Flole998]

Similar to #2501 there is an issue in

openhab-core/bundles/org.openhab.core.ui.icon/src/main/java/org/openhab/core/ui/icon/internal/IconServlet.java

Line 153 in 9d9dc70

try (InputStream is = provider.getIcon(category, iconSetId, state, format)) {

causing an exception in case there is an issue:

java.lang.IllegalStateException: ABORTED
        at org.eclipse.jetty.server.HttpChannelState.sendError(HttpChannelState.java:915) ~[?:?]
        at org.eclipse.jetty.server.Response.sendError(Response.java:471) ~[?:?]
        at org.openhab.core.ui.icon.internal.IconServlet.doGet(IconServlet.java:163) ~[?:?]
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:687) ~[bundleFile:3.1.0]
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:790) ~[bundleFile:3.1.0]
        at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:799) ~[?:?]
        at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:550) ~[?:?]
        at org.ops4j.pax.web.service.jetty.internal.HttpServiceServletHandler.doHandle(HttpServiceServletHandler.java:71) ~[?:?]
        at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:143) ~[bundleFile:9.4.43.v20210629]
        at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:602) ~[?:?]
        at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:127) ~[bundleFile:9.4.43.v20210629]
        at org.eclipse.jetty.server.handler.ScopedHandler.nextHandle(ScopedHandler.java:235) ~[bundleFile:9.4.43.v20210629]
        at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:1624) ~[bundleFile:9.4.43.v20210629]
        at org.eclipse.jetty.server.handler.ScopedHandler.nextHandle(ScopedHandler.java:233) ~[bundleFile:9.4.43.v20210629]
        at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1434) ~[bundleFile:9.4.43.v20210629]
        at org.ops4j.pax.web.service.jetty.internal.HttpServiceContext.doHandle(HttpServiceContext.java:294) ~[?:?]
        at org.eclipse.jetty.server.handler.ScopedHandler.nextScope(ScopedHandler.java:188) ~[bundleFile:9.4.43.v20210629]
        at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:501) ~[?:?]
        at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:1594) ~[bundleFile:9.4.43.v20210629]
        at org.eclipse.jetty.server.handler.ScopedHandler.nextScope(ScopedHandler.java:186) ~[bundleFile:9.4.43.v20210629]
        at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1349) ~[bundleFile:9.4.43.v20210629]
        at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:141) ~[bundleFile:9.4.43.v20210629]
        at org.ops4j.pax.web.service.jetty.internal.JettyServerHandlerCollection.handle(JettyServerHandlerCollection.java:82) ~[?:?]
        at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:127) ~[bundleFile:9.4.43.v20210629]
        at org.eclipse.jetty.server.Server.handle(Server.java:516) ~[bundleFile:9.4.43.v20210629]
        at org.eclipse.jetty.server.HttpChannel.lambda$handle$1(HttpChannel.java:388) ~[bundleFile:9.4.43.v20210629]
        at org.eclipse.jetty.server.HttpChannel.dispatch(HttpChannel.java:633) ~[bundleFile:9.4.43.v20210629]
        at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:380) [bundleFile:9.4.43.v20210629]
        at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:277) [bundleFile:9.4.43.v20210629]
        at org.eclipse.jetty.io.AbstractConnection$ReadCallback.succeeded(AbstractConnection.java:311) [bundleFile:9.4.43.v20210629] 
        at org.eclipse.jetty.io.FillInterest.fillable(FillInterest.java:105) [bundleFile:9.4.43.v20210629]
        at org.eclipse.jetty.io.ChannelEndPoint$1.run(ChannelEndPoint.java:104) [bundleFile:9.4.43.v20210629]
        at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.runTask(EatWhatYouKill.java:338) [bundleFile:9.4.43.v20210629]
        at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.doProduce(EatWhatYouKill.java:315) [bundleFile:9.4.43.v20210629]
        at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.tryProduce(EatWhatYouKill.java:173) [bundleFile:9.4.43.v20210629]
        at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.run(EatWhatYouKill.java:131) [bundleFile:9.4.43.v20210629]
        at org.eclipse.jetty.util.thread.ReservedThreadExecutor$ReservedThread.run(ReservedThreadExecutor.java:386) [bundleFile:9.4.43.v20210629]
        at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:883) [bundleFile:9.4.43.v20210629]
        at org.eclipse.jetty.util.thread.QueuedThreadPool$Runner.run(QueuedThreadPool.java:1034) [bundleFile:9.4.43.v20210629]
        at java.lang.Thread.run(Thread.java:829) [?:?]

The getOutputStream() should only be called after we know for sure if we want to write a response or send an error, in this case that would be in line 159 before doing the transferTo() call.