Java: Don't offer "Unwrap 'else' branch" intention if it might cause unreachable code (IDEA-165428)

java/java-tests/testData/codeInsight/unwrapElseBranch/beforeSwitch3.java

@@ -0,0 +1,19 @@
+// "Unwrap 'else' branch (changes semantics)" "true"
+
+class T {
+    void f(boolean b, int n) {
+        switch (n) {
+            case 1:
+                if (b)
+                    System.out.println("When true");
+                <caret>else {
+                    // Before
+                    System.out.println("Otherwise");
+                    // After
+                    return;
+                }
+            case 2:
+        }
+        System.out.println("Done");
+    }
+}