infer nullity: check for switch conditions (IDEA-61451)

java/java-tests/testData/codeInsight/nullityinferrer/afterTryEnumSwitch.java

@@ -0,0 +1,13 @@
+import org.jetbrains.annotations.*;
+
+public class Infer {
+    enum E {;
+    }
+
+    void trySwitchEnum(@NotNull E e) {
+        switch (e) {
+
+        }
+    }
+
+}