fix(viewer): show the modal when it carries only an error

__tests__/component/Viewer.spec.ts

@@ -87,15 +87,17 @@ describe('Viewer.open()', () => {
 	})
 
 	it('shows an error when the explicit handlerId is not registered', async () => {
-		const { vm, wrapper, errorText, modalProps } = mountViewer([imageHandler()])
+		const { vm, wrapper, errorText, modalProps, renderedTags } = mountViewer([imageHandler()])
 		const f1 = makeFile({ mime: 'image/jpeg' })
 
 		await vm.open([f1], f1, undefined, 'does-not-exist')
 		await wrapper.vm.$nextTick()
 
 		expect(errorText()).toBe('There was no plugin available to open this file.')
-		// No file got opened.
-		expect(modalProps().show).toBe(false)
+		// No file got opened, but the modal is shown regardless: it is what
+		// carries the error, and it hides its content while `show` is false.
+		expect(renderedTags()).toEqual([])
+		expect(modalProps().show).toBe(true)
 	})
 
 	it.each([

__tests__/component/mountViewer.ts

@@ -40,6 +40,7 @@ export const NcModalStub = defineComponent({
 	emits: ['next', 'previous', 'close'],
 	template: `
 		<div
+			v-show="show"
 			class="nc-modal-stub"
 			:style="$attrs.style"
 			:data-handler="$attrs['data-handler']"
@@ -203,8 +204,11 @@ export function mountViewer(handlers: IHandler[] = []): MountViewerResult {
 		modalExists: () => findModal().exists(),
 		renderedTags,
 		errorText: () => {
+			// The real modal hides its content with `v-show`, which the stub
+			// mirrors: an error inside a modal that is not shown is an error
+			// nobody can read, so it does not count as being reported.
 			const ec = wrapper.find('.nc-empty-content-stub')
-			return ec.exists() ? ec.attributes('data-name') : undefined
+			return ec.exists() && ec.isVisible() ? ec.attributes('data-name') : undefined
 		},
 	}
 }

lib/views/Viewer.vue

@@ -20,7 +20,7 @@
 		:inlineActions="canEdit ? 1 : 0"
 		:lightBackdrop="lightBackdrop"
 		:name="modalName"
-		:show="!!currentFile"
+		:show="!!currentFile || !!errorString"
 		:slideshowPaused="editing"
 		:spreadNavigation="true"
 		:style="{ width: isSidebarShown ? `${sidebarPosition}px` : null }"