fix: avoid empty column when HEAD is filtered out

Author: heartacker

src/Models/CommitGraph.cs

@@ -110,7 +110,7 @@ public static CommitGraph Parse(List<Commit> commits, bool firstParentOnlyEnable
 
                 // 2. Reserve leftmost column (offsetX) for HEAD path if not yet found
                 var offsetX = 4 - halfWidth;
-                if (alwaysShowCurrentHeadOnLeft && headPath == null)
+                if (alwaysShowCurrentHeadOnLeft && headPath == null && headPathSHAs.Count > 0)
                     offsetX += unitWidth;
 
                 // 3. Keep track of max offsetX used in previous rows for margin calculation