Minor: Fix compilation-breaking nullability issues

idea/src/org/jetbrains/kotlin/idea/refactoring/changeSignature/JetChangeSignatureProcessor.kt

@@ -29,6 +29,7 @@ import com.intellij.refactoring.rename.RenameUtil
 import com.intellij.usageView.UsageInfo
 import com.intellij.usageView.UsageViewDescriptor
 import com.intellij.util.containers.MultiMap
+import org.jetbrains.annotations.NotNull
 import org.jetbrains.kotlin.idea.refactoring.changeSignature.usages.JetUsageInfo
 import org.jetbrains.kotlin.idea.refactoring.changeSignature.usages.KotlinWrapperForJavaUsageInfos
 import java.util.*
@@ -101,7 +102,7 @@ public class JetChangeSignatureProcessor(project: Project,
         return true
     }
 
-    override fun isPreviewUsages(usages: Array<UsageInfo>?) = isPreviewUsages()
+    override fun isPreviewUsages(NotNull usages: Array<out UsageInfo>): Boolean = isPreviewUsages()
 
     override fun getCommandName() = commandName
 }

idea/src/org/jetbrains/kotlin/idea/refactoring/changeSignature/ui/JetChangeSignatureDialog.kt

@@ -406,7 +406,7 @@ public class JetChangeSignatureDialog(
         private fun evaluateChangeInfo(parametersModel: JetCallableParameterTableModel,
                                        returnTypeCodeFragment: PsiCodeFragment?,
                                        methodDescriptor: JetMethodDescriptor,
-                                       visibility: Visibility,
+                                       visibility: Visibility?,
                                        methodName: String,
                                        defaultValueContext: PsiElement): JetChangeInfo {
             val parameters = parametersModel.getItems().map { parameter ->
@@ -428,7 +428,7 @@ public class JetChangeSignatureDialog(
                                  methodName,
                                  returnType,
                                  returnTypeText,
-                                 visibility,
+                                 visibility ?: Visibilities.INTERNAL,
                                  parameters,
                                  parametersModel.getReceiver(),
                                  defaultValueContext)