Evaluate expression: fix exception when default package is used

#KT-5555 Fixed

idea/src/org/jetbrains/jet/plugin/debugger/evaluate/KotlinEvaluationBuilder.kt

@@ -78,7 +78,7 @@ object KotlinEvaluationBuilder: EvaluatorBuilder {
         }
 
         val packageName = file.getPackageDirective()?.getFqName()?.asString()
-        if (packageName != null) {
+        if (packageName != null && packageName.isNotEmpty()) {
             codeFragment.addImportsFromString("import $packageName.*")
         }
         return ExpressionEvaluatorImpl(KotlinEvaluator(codeFragment as JetCodeFragment, position))

idea/testData/debugger/tinyApp/outs/_kt.out

@@ -0,0 +1,8 @@
+LineBreakpoint created at .kt.kt:5
+!JDK_HOME!\bin\java -agentlib:jdwp=transport=dt_socket,address=!HOST_NAME!:!HOST_PORT!,suspend=y,server=n -Dfile.encoding=!FILE_ENCODING! -classpath !APP_PATH!\classes;!KOTLIN_RUNTIME!;!RT_JAR! _DefaultPackage
+Connected to the target VM, address: '!HOST_NAME!:PORT_NAME!', transport: 'socket'
+.kt.kt:4
+Compile bytecode for 1 + 1
+Disconnected from the target VM, address: '!HOST_NAME!:PORT_NAME!', transport: 'socket'
+
+Process finished with exit code 0

idea/testData/debugger/tinyApp/src/evaluate/singleBreakpoint/.kt.kt

@@ -0,0 +1,9 @@
+// Test evaluate expression for default package
+
+fun main(args: Array<String>) {
+    //Breakpoint!
+    args.size
+}
+
+// EXPRESSION: 1 + 1
+// RESULT: 2: I

idea/tests/org/jetbrains/jet/plugin/debugger/evaluate/KotlinEvaluateExpressionTestGenerated.java

@@ -138,6 +138,11 @@ public class KotlinEvaluateExpressionTestGenerated extends AbstractKotlinEvaluat
             doSingleBreakpointTest("idea/testData/debugger/tinyApp/src/evaluate/singleBreakpoint/vars.kt");
         }
         
+        @TestMetadata(".kt.kt")
+        public void test_kt() throws Exception {
+            doSingleBreakpointTest("idea/testData/debugger/tinyApp/src/evaluate/singleBreakpoint/.kt.kt");
+        }
+        
     }
     
     @TestMetadata("idea/testData/debugger/tinyApp/src/evaluate/multipleBreakpoints")