Eliminate a set of warnings, mostly nullability ones

idea/ide-common/src/org/jetbrains/kotlin/idea/util/CallType.kt

@@ -278,8 +278,6 @@ fun CallTypeAndReceiver<*, *>.receiverTypesWithIndex(
         is CallTypeAndReceiver.ANNOTATION,
         is CallTypeAndReceiver.UNKNOWN ->
             return null
-
-        else -> throw RuntimeException() //TODO: see KT-9394
     }
 
     val resolutionScope = contextElement.getResolutionScope(bindingContext, resolutionFacade)

idea/ide-common/src/org/jetbrains/kotlin/util/descriptorUtils.kt

@@ -73,7 +73,7 @@ fun ClassDescriptor.findCallableMemberBySignature(
                 if (it.containingDeclaration != this) return@firstOrNull false
                 val overridability = OverridingUtil.DEFAULT.isOverridableBy(it as CallableDescriptor, signature, null).result
                 overridability == OVERRIDABLE || (allowOverridabilityConflicts && overridability == CONFLICT)
-            } as? CallableMemberDescriptor
+            }
 }
 
 fun TypeConstructor.supertypesWithAny(): Collection<KotlinType> {