Qute Type-safe Templates - fix template path validation

[mkouba]

• also add more meaningful error message if a template matches the path
  but the file suffix is not configured via quarkus.qute.suffixes
• resolves NullPointerException when rendering Qute templates as XML  #12355

[gastaldi]

LGTM

[gsmet]

CI failed with:

2021-03-02T19:22:51.8960176Z [ERROR] io.quarkus.resteasy.reactive.qute.deployment.MissingTemplateTest  Time elapsed: 0.807 s  <<< FAILURE!
2021-03-02T19:22:51.8962316Z java.lang.AssertionError: COM01003: Internal error: Assertion failure: Expected boolean value to be false
2021-03-02T19:22:51.8963621Z 	at org.wildfly.common.Assert.assertTrue(Assert.java:520)
2021-03-02T19:22:51.8966057Z 	at io.quarkus.resteasy.reactive.qute.deployment.MissingTemplateTest.lambda$static$1(MissingTemplateTest.java:20)
2021-03-02T19:22:51.8968705Z 	at io.quarkus.test.QuarkusUnitTest.beforeAll(QuarkusUnitTest.java:490)
2021-03-02T19:22:51.8971857Z 	at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.lambda$invokeBeforeAllCallbacks$8(ClassBasedTestDescriptor.java:368)
2021-03-02T19:22:51.8975676Z 	at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
2021-03-02T19:22:51.9032805Z 	at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.invokeBeforeAllCallbacks(ClassBasedTestDescriptor.java:368)
2021-03-02T19:22:51.9037146Z 	at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.before(ClassBasedTestDescriptor.java:192)
2021-03-02T19:22:51.9040649Z 	at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.before(ClassBasedTestDescriptor.java:78)
2021-03-02T19:22:51.9044035Z 	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:136)
2021-03-02T19:22:51.9047504Z 	at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)

[gsmet]

Btw, we shouldn't use org.wildfly.common.Assert.

[mkouba]

Btw, we shouldn't use org.wildfly.common.Assert.

Sure thing. I'm not the original author of the test though ;-).

The test should be fixed now.