fix: more robust tags parsing

quartz/plugins/transformers/frontmatter.ts

@@ -49,11 +49,19 @@ export const FrontMatter: QuartzTransformerPlugin<Partial<Options> | undefined>
               data.title = file.stem ?? "Untitled"
             }
 
-            if (data.tags && !Array.isArray(data.tags)) {
+            if (data.tags) {
+              // coerce to array
+              if (!Array.isArray(data.tags)) {
+                data.tags = data.tags
+                  .toString()
+                  .split(oneLineTagDelim)
+                  .map((tag: string) => tag.trim())
+              }
+
+              // remove all non-string tags
               data.tags = data.tags
-                .toString()
+                .filter((tag: unknown) => typeof tag === "string" || typeof tag === "number")
-                .split(oneLineTagDelim)
+                .map((tag: string | number) => tag.toString())
-                .map((tag: string) => tag.trim())
             }
 
             // slug them all!!