toString() on nullables fixed

compiler/frontend/src/org/jetbrains/jet/lang/evaluate/ConstantExpressionEvaluator.kt

@@ -554,7 +554,7 @@ private fun createStringConstant(value: CompileTimeConstant<*>?): StringValue? {
         is CharValue,
         is DoubleValue, is FloatValue,
         is BooleanValue,
-        is NullValue -> StringValue(value.getValue().toString(), value.canBeUsedInAnnotations(), value.usesVariableAsConstant())
+        is NullValue -> StringValue("${value.getValue()}", value.canBeUsedInAnnotations(), value.usesVariableAsConstant())
         else -> null
     }
 }

compiler/tests/org/jetbrains/jet/evaluate/AbstractEvaluateExpressionTest.kt

@@ -43,7 +43,7 @@ public abstract class AbstractEvaluateExpressionTest : AbstractAnnotationDescrip
             if (compileTimeConstant is StringValue) {
                 "\\\"${compileTimeConstant.getValue()}\\\""
             } else {
-                compileTimeConstant.toString()
+                "$compileTimeConstant"
             }
         }
     }