[@astrojs/image] Handle missing trailing slash in processStaticImage (#…

…6421)

The code path changed by this commit isn't only taken when running using Vite. If the site is configured with a base url which is different from `/` but does **not** end with `/` (for example, because `trailingSlash` is set to `never`), the `- 1` results in an off-by-one error when truncating the URL.

By checking if the base url ends with `/`, we can determine the right length for the prefix to truncate.

.changeset/eleven-mugs-flash.md

@@ -0,0 +1,5 @@
+---
+'@astrojs/image': patch
+---
+
+Handle missing trailing slash in processStaticImage

packages/integrations/image/src/build/ssg.ts

@@ -138,7 +138,7 @@ export async function ssgBuild({
 		// Vite will prefix a hashed image with the base path, we need to strip this
 		// off to find the actual file relative to /dist
 		if (config.base && src.startsWith(config.base)) {
-			src = src.substring(config.base.length - 1);
+			src = src.substring(config.base.length - +config.base.endsWith('/'));
 		}
 
 		if (isRemoteImage(src)) {