CreateDraftComment: Allow line 0

This is used for a file comment. The corresponding check in
PutDraftComment already supports line == 0.

Change-Id: I54fb6c80f021e9e5b12acf492cab646da698ae11
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/change/CreateDraftComment.java b/gerrit-server/src/main/java/com/google/gerrit/server/change/CreateDraftComment.java
index 6b8d8db..8e124b2 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/change/CreateDraftComment.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/change/CreateDraftComment.java
@@ -76,8 +76,8 @@
       throw new BadRequestException("path must be non-empty");
     } else if (in.message == null || in.message.trim().isEmpty()) {
       throw new BadRequestException("message must be non-empty");
-    } else if (in.line != null && in.line <= 0) {
-      throw new BadRequestException("line must be > 0");
+    } else if (in.line != null && in.line < 0) {
+      throw new BadRequestException("line must be >= 0");
     } else if (in.line != null && in.range != null && in.line != in.range.endLine) {
       throw new BadRequestException("range endLine must be on the same line as the comment");
     }