Issue 4354. Fix for NPE when switch/case has no expression

compiler/java/com/google/dart/compiler/type/TypeAnalyzer.java

Index: compiler/java/com/google/dart/compiler/type/TypeAnalyzer.java
diff --git a/compiler/java/com/google/dart/compiler/type/TypeAnalyzer.java b/compiler/java/com/google/dart/compiler/type/TypeAnalyzer.java
index 1c11c7ea8425c67921bcd53386f6551b6299b1da..70d4b7d802a5d912c7a4f44a9662fde62351f926 100644
--- a/compiler/java/com/google/dart/compiler/type/TypeAnalyzer.java
+++ b/compiler/java/com/google/dart/compiler/type/TypeAnalyzer.java
@@ -2129,6 +2129,10 @@ public class TypeAnalyzer implements DartCompilationPhase {
         if (switchMember instanceof DartCase) {
           DartCase caseMember = (DartCase) switchMember;
           DartExpression caseExpr = caseMember.getExpr();
+          // no expression, parser already reported about this
+          if (caseExpr == null) {
+            continue;
+          }
           Type caseType = nonVoidTypeOf(caseExpr);
           // should be "int" or "String"
           if (!Objects.equal(caseType, intType) && !Objects.equal(caseType, stringType)) {