navigation: don't show notification that nothing was found after cancel of the modal progress (IDEA-157671)

platform/lang-impl/src/com/intellij/codeInsight/navigation/CtrlMouseHandler.java

@@ -571,6 +571,9 @@ public class CtrlMouseHandler extends AbstractProjectComponent {
           return PsiUtilCore.toPsiElementArray(found);
         }
       }.searchImplementations(editor, element, offset);
+      if (targetElements == null) {
+        return null;
+      }
       if (targetElements.length > 1) {
         PsiElement elementAtPointer = file.findElementAt(offset);
         if (elementAtPointer != null) {

platform/lang-impl/src/com/intellij/codeInsight/navigation/GotoImplementationHandler.java

@@ -61,6 +61,7 @@ public class GotoImplementationHandler extends GotoTargetHandler {
         return false;
       }
     }.searchImplementations(editor, source, offset);
+    if (targets == null) return null;
     GotoData gotoData = new GotoData(source, targets, Collections.emptyList());
     gotoData.listUpdaterTask = new ImplementationsUpdaterTask(gotoData, editor, offset, reference);
     return gotoData;

platform/lang-impl/src/com/intellij/codeInsight/navigation/ImplementationSearcher.java

@@ -40,7 +40,7 @@ public class ImplementationSearcher {
 
   public static final String SEARCHING_FOR_IMPLEMENTATIONS = CodeInsightBundle.message("searching.for.implementations");
 
-  @NotNull
+  @Nullable
   PsiElement[] searchImplementations(final Editor editor, final PsiElement element, final int offset) {
     final TargetElementUtil targetElementUtil = TargetElementUtil.getInstance();
     boolean onRef = ApplicationManager.getApplication().runReadAction(new Computable<Boolean>() {
@@ -57,14 +57,14 @@ public class ImplementationSearcher {
     }), onRef);
   }
 
-  @NotNull
+  @Nullable
   public PsiElement[] searchImplementations(final PsiElement element,
                                             final Editor editor, final int offset,
                                             final boolean includeSelfAlways,
                                             final boolean includeSelfIfNoOthers) {
     if (element == null) return PsiElement.EMPTY_ARRAY;
     final PsiElement[] elements = searchDefinitions(element, editor);
-    if (elements == null) return PsiElement.EMPTY_ARRAY; //the search has been cancelled
+    if (elements == null) return null; //the search has been cancelled
     if (elements.length > 0) {
       if (!includeSelfAlways) return filterElements(element, elements, offset);
       final PsiElement[] all;