[NI] Report unsafe invoke properly for flexible types

`isNullable` check returns `true` for flexible types,
which leads to false positive unsafe invoke error, when
receiver for invoke's property is flexible.
^KT-30695 Fixed

compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/components/ResolutionParts.kt

@@ -343,7 +343,7 @@ private fun KotlinResolutionCandidate.checkUnsafeImplicitInvokeAfterSafeCall(arg
         }
     } ?: error("Receiver kind does not match receiver argument")
 
-    if (receiverArgument.receiver.stableType.isNullable()) {
+    if (receiverArgument.isSafeCall && receiverArgument.receiver.stableType.isNullable()) {
         addDiagnostic(UnsafeCallError(argument, isForImplicitInvoke = true))
         return ImplicitInvokeCheckStatus.UNSAFE_INVOKE_REPORTED
     }