Added assert clarification for EA-66572

Author: Evgeny Gerashchenko

idea/src/org/jetbrains/kotlin/idea/inspections/UnusedSymbolInspection.kt

@@ -166,6 +166,7 @@ public class UnusedSymbolInspection : AbstractKotlinInspection() {
             var zeroOccurrences = true
 
             for (name in listOf(declaration.getName()) + declaration.getAccessorNames() + declaration.getClassNameForCompanionObject().singletonOrEmptyList()) {
+                assert(name != null) { "Name is null for " + JetPsiUtil.getElementTextWithContext(declaration) }
                 when (psiSearchHelper.isCheapEnoughToSearch(name, useScope, null, null)) {
                     ZERO_OCCURRENCES -> {} // go on, check other names
                     FEW_OCCURRENCES -> zeroOccurrences = false