Correct retrieval of LastTagTime when the Docker image doesn't already exist

tests/docker/src/lib.rs

@@ -39,12 +39,14 @@ pub fn build(name: String) {
     .arg(format!("serai-dev-{name}"))
     .output()
   {
+    let last_tag_time_buf = String::from_utf8(res.stdout).expect("docker had non-utf8 output");
+    let last_tag_time = last_tag_time_buf.trim();
+    if !last_tag_time.is_empty() {
       let created_time = SystemTime::from(
-      chrono::DateTime::parse_and_remainder(
-        String::from_utf8(res.stdout).expect("docker had non-utf8 output").trim(),
-        "%F %T.%f %z",
-      )
-      .expect("docker formatted last tag time unexpectedly")
+        chrono::DateTime::parse_and_remainder(last_tag_time, "%F %T.%f %z")
+          .unwrap_or_else(|_| {
+            panic!("docker formatted last tag time unexpectedly: {last_tag_time}")
+          })
           .0,
       );
 
@@ -92,11 +94,12 @@ pub fn build(name: String) {
               }
             }
           } else {
-          // Recursively crawl since we care when the folder's contents were edited, not the folder
-          // itself
+            // Recursively crawl since we care when the folder's contents were edited, not the
+            // folder itself
             for entry in fs::read_dir(path.clone()).expect("couldn't read directory") {
-            metadatas
-              .push(meta(path.join(entry.expect("couldn't access item in directory").file_name())));
+              metadatas.push(meta(
+                path.join(entry.expect("couldn't access item in directory").file_name()),
+              ));
             }
           }
         }
@@ -110,6 +113,7 @@ pub fn build(name: String) {
         }
       }
     }
+  }
 
   println!("Building {}...", &name);