do not create throws list without exceptions (IDEA-65790 )

java/java-impl/src/com/intellij/psi/impl/PsiElementFactoryImpl.java

@@ -402,7 +402,10 @@ public class PsiElementFactoryImpl extends PsiJavaParserFacadeImpl implements Ps
   public PsiReferenceList createReferenceList(@NotNull final PsiJavaCodeReferenceElement[] references) throws IncorrectOperationException {
     final StringBuilder builder = StringBuilderSpinAllocator.alloc();
     try {
-      builder.append("void method() throws ");
+      builder.append("void method()");
+      if (references.length > 0){
+        builder.append(" throws ");
+      }
       for (int i = 0; i < references.length; i++) {
         if (i > 0) builder.append(", ");
         builder.append(references[i].getCanonicalText());

java/java-tests/testData/refactoring/changeSignature/RemoveExceptions.java

@@ -0,0 +1,4 @@
+class Test {
+  void fo<caret>o() throws RuntimeException {
+  }
+}

java/java-tests/testData/refactoring/changeSignature/RemoveExceptions_after.java

@@ -0,0 +1,4 @@
+class Test {
+  void foo() {
+  }
+}

java/java-tests/testSrc/com/intellij/refactoring/ChangeSignatureTest.java

@@ -288,6 +288,10 @@ public class ChangeSignatureTest extends LightCodeInsightTestCase {
     doTest(null, null, "Exception", new SimpleParameterGen(), new SimpleExceptionsGen(), false);
   }
 
+  public void testRemoveExceptions() throws Exception {
+    doTest(null, null, "void", new SimpleParameterGen(), new SimpleExceptionsGen(), false);
+  }
+
   private void doTest(String newReturnType, ParameterInfoImpl[] parameterInfos, final boolean generateDelegate) throws Exception {
     doTest(null, null, newReturnType, parameterInfos, new ThrownExceptionInfo[0], generateDelegate);
   }