Rule 6.4.1: Avoid using utility classes/objects

diktat-rules/src/main/kotlin/org/cqfn/diktat/ruleset/rules/AvoidUtilityClass.kt

@@ -55,6 +55,6 @@ class AvoidUtilityClass(private val configRules: List<RulesConfig>) : Rule("avoi
                 ?.filter { it.elementType == FUN }
                 ?.ifEmpty { return }
                 ?: return
-        AVOID_USING_UTILITY_CLASS.warn(configRules, emitWarn, isFixMode, node.findChildByType(IDENTIFIER)!!.text, node.startOffset, node)
+        AVOID_USING_UTILITY_CLASS.warn(configRules, emitWarn, isFixMode, node.findChildByType(IDENTIFIER)?.text ?: node.text, node.startOffset, node)
     }
 }

diktat-rules/src/test/kotlin/org/cqfn/diktat/ruleset/chapter6/AvoidUtilityClassWarnTest.kt

@@ -79,4 +79,21 @@ class AvoidUtilityClassWarnTest: LintTestBase(::AvoidUtilityClass) {
                 LintError(2,1, ruleId, "${AVOID_USING_UTILITY_CLASS.warnText()} StringUtils")
         )
     }
+
+    @Test
+    @Tag(WarningNames.AVOID_USING_UTILITY_CLASS)
+    fun `test with class without identifier`() {
+        lintMethod(
+                """
+                    fun foo() {
+                    window.addMouseListener(object : MouseAdapter() {
+                        override fun mouseClicked(e: MouseEvent) { /*...*/ }
+
+                        override fun mouseEntered(e: MouseEvent) { /*...*/ }
+                    })
+                    }
+                """.trimMargin(),
+                LintError(2,45, ruleId, "${AVOID_USING_UTILITY_CLASS.warnText()} object : MouseAdapter() {...")
+        )
+    }
 }