Avoid null type, derive from provider type params or fallback to Object.

[sdedic]

This fixes a potential NPE thrown in some situations:

Cannot invoke "java.lang.Class.getModifiers()" because "clazz" is null
Error stack trace: org.netbeans.modules.gradle.tooling.NbProjectInfoBuilder.findNonDecoratedClass(NbProjectInfoBuilder.java:943)
org.netbeans.modules.gradle.tooling.NbProjectInfoBuilder.inspectObjectAndValues0(NbProjectInfoBuilder.java:746)
org.netbeans.modules.gradle.tooling.NbProjectInfoBuilder.inspectObjectAndValues(NbProjectInfoBuilder.java:597)
org.netbeans.modules.gradle.tooling.NbProjectInfoBuilder.startInspectObjectAndValues(NbProjectInfoBuilder.java:563)
org.netbeans.modules.gradle.tooling.NbProjectInfoBuilder.detectTaskProperties(NbProjectInfoBuilder.java:320)
org.netbeans.modules.gradle.tooling.NbProjectInfoBuilder.lambda$runAndRegisterPerf$7(NbProjectInfoBuilder.java:427)
org.netbeans.modules.gradle.tooling.NbProjectInfoBuilder.runAndRegisterPerf(NbProjectInfoBuilder.java:433)
org.netbeans.modules.gradle.tooling.NbProjectInfoBuilder.runAndRegisterPerf(NbProjectInfoBuilder.java:427)
org.netbeans.modules.gradle.tooling.NbProjectInfoBuilder.lambda$buildAll$3(NbProjectInfoBuilder.java:248)
org.netbeans.modules.gradle.tooling.NbProjectInfoBuilder.sinceGradle(NbProjectInfoBuilder.java:1850)

With micronaut-core, null is sometimes returned by the provider as a value, and the (Provider) type in t is overwritten by null and subsequently fails in findNonDecoratedClass. Even when getFixedValue()returns != null, the provider'sgetType()sometimes returnsnull` as a type - added a fallback to actual value's Class.

Lastly, if it is not possible to determien type from either a concrete value, or the provider's type parameter, the introspection falls back to Object.class.

[sdedic]

If no objections are raised, will merge later today.

[lahodaj]

Not really an expert here, but makes sense to me.