Fix spam filtering when the score is negative

dovecot/sieve/before.sieve

@@ -9,13 +9,14 @@ require "relational";
 require "comparator-i;ascii-numeric";
 require "vnd.dovecot.extdata";
 
-if string :is "${extdata.spam_enabled}" "1" {
-  if header :matches "X-Spam-Status" "* score=*" {
-    if string :value "ge" :comparator "i;ascii-numeric" "${2}" "${extdata.spam_threshold}" {
-      setflag "\\seen";
-      fileinto :create "Junk";
-      stop;
-    }
+if allof (string :is "${extdata.spam_enabled}" "1",
+          not header :matches "X-Spam-Status" "* score=-*",
+          header :matches "X-Spam-Status" "* score=*")
+{
+  if string :value "ge" :comparator "i;ascii-numeric" "${2}" "${extdata.spam_threshold}" {
+    setflag "\\seen";
+    fileinto :create "Junk";
+    stop;
   }
 }