Fixed selection in case of empty class body

#KT-30597 Fixed

idea/src/org/jetbrains/kotlin/idea/editor/wordSelection/KotlinClassMemberSelectioner.kt

@@ -24,7 +24,10 @@ class KotlinClassMemberSelectioner : ExtendWordSelectionHandlerBase() {
         val lastChild = parent.lastChild ?: return null
         val startElement = firstChild.getNextSiblingIgnoringWhitespace() ?: firstChild
         val endElement = lastChild.getPrevSiblingIgnoringWhitespace() ?: lastChild
-        val textRange = TextRange(startElement.textRange.startOffset, endElement.textRange.endOffset)
+        val startOffset = startElement.textRange.startOffset
+        val endOffset = endElement.textRange.endOffset
+        if (startOffset >= endOffset) return null
+        val textRange = TextRange(startOffset, endOffset)
         return expandToWholeLinesWithBlanks(editorText, textRange)
     }
 }

idea/testData/wordSelection/Class/0.kt

@@ -0,0 +1,3 @@
+class SimpleClass {
+    <caret>
+}

idea/testData/wordSelection/Class/1.kt

@@ -0,0 +1,3 @@
+class SimpleClass <selection>{
+    <caret>
+}</selection>

idea/testData/wordSelection/Class/2.kt

@@ -0,0 +1,3 @@
+<selection>class SimpleClass {
+    <caret>
+}</selection>

idea/tests/org/jetbrains/kotlin/idea/WordSelectionTest.java

@@ -112,6 +112,10 @@ public class WordSelectionTest extends KotlinLightCodeInsightFixtureTestCase {
         doTest();
     }
 
+    public void testClass() {
+        doTest();
+    }
+
     public void testDeclarationWithComment1() { doTest(); }
     public void testDeclarationWithComment2() { doTest(); }
     public void testDeclarationWithComment3() { doTest(); }