Fix NPE in checkLValue when selector is absent. Add test for incomplete syntax.

compiler/frontend/src/org/jetbrains/kotlin/types/expressions/BasicExpressionTypingVisitor.java

@@ -913,8 +913,11 @@ public class BasicExpressionTypingVisitor extends ExpressionTypingVisitor {
 
         boolean result = true;
         JetExpression reportOn = expression != null ? expression : expressionWithParenthesis;
-        if (reportOn instanceof JetQualifiedExpression)
+        if (reportOn instanceof JetQualifiedExpression) {
-            reportOn = ((JetQualifiedExpression)reportOn).getSelectorExpression();
+            JetExpression selector = ((JetQualifiedExpression) reportOn).getSelectorExpression();
+            if (selector != null)
+                reportOn = selector;
+        }
 
         if (variable instanceof PropertyDescriptor) {
             PropertyDescriptor propertyDescriptor = (PropertyDescriptor) variable;

compiler/testData/diagnostics/tests/LValueAssignment.kt

@@ -91,6 +91,11 @@ class Test() {
         s += (a@ 2)
     }
 
+    fun testIncompleteSyntax() {
+        val s = "s"
+        <!DEBUG_INFO_ELEMENT_WITH_ERROR_TYPE!>++<!>s.<!SYNTAX!><!>
+    }
+
     fun testVariables() {
         var a: Int = 34
         val b: Int = 34

compiler/testData/diagnostics/tests/LValueAssignment.txt

@@ -67,6 +67,7 @@ package lvalue_assignment {
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         internal final fun testArrays(/*0*/ a: kotlin.Array<kotlin.Int>, /*1*/ ab: lvalue_assignment.Ab): kotlin.Unit
         internal final fun testIllegalValues(): kotlin.Unit
+        internal final fun testIncompleteSyntax(): kotlin.Unit
         internal final fun testVariables(): kotlin.Unit
         internal final fun testVariables1(): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String