FIR: fix a bunch of issues after DiagnosticsReporter refactoring related to reporting diagnostic on null source

compiler/testData/diagnostics/testsWithStdLib/experimental/implicitUsages.fir.kt

@@ -85,7 +85,7 @@ object O {
     operator fun provideDelegate(x: Any?, y: Any?): C = C()
 }
 
-val x: String by <!OPT_IN_USAGE_ERROR!>O<!>
+val x: String by <!OPT_IN_USAGE_ERROR, OPT_IN_USAGE_ERROR!>O<!>
 
 @Marker
 class OperatorContainer : Comparable<OperatorContainer> {
@@ -122,4 +122,4 @@ fun operatorContainerUsage(s: String, a: AnotherContainer) {
     val res2 = <!OPT_IN_USAGE_ERROR!>s<!>()
     val res3 = <!OPT_IN_USAGE_ERROR!>res1<!> <!OPT_IN_USAGE_ERROR!>><!> <!OPT_IN_USAGE_ERROR!>res2<!>
     <!OPT_IN_USAGE_ERROR, OPT_IN_USAGE_ERROR, OPT_IN_USAGE_ERROR, OPT_IN_USAGE_ERROR, OPT_IN_USAGE_ERROR!>for (c in a) {}<!>
-}
+}