修复空帧导致的包围盒计算错误

Spine/SpineExtension.cs

@@ -110,6 +110,8 @@ namespace Spine
                         break;
                 }
 
+                if (verticesLength > 0)
+                {
                     for (int ii = 0; ii + 1 < verticesLength; ii += 2)
                     {
                         float vx = vertices[ii];
@@ -120,11 +122,31 @@ namespace Spine
                         maxY = Math.Max(maxY, vy);
                     }
                 }
+                else
+                {
+                    var boneX = slot.Bone.WorldX;
+                    var boneY = slot.Bone.WorldY;
+                    minX = Math.Min(minX, boneX);
+                    minY = Math.Min(minY, boneY);
+                    maxX = Math.Max(maxX, boneX);
+                    maxY = Math.Max(maxY, boneY);
+                }
+            }
+            if (minX >= int.MaxValue || minY >= int.MaxValue || maxX <= int.MinValue || maxY <= int.MinValue)
+            {
+                x = self.X;
+                y = self.Y;
+                w = 0;
+                h = 0;
+            }
+            else
+            {
                 x = minX;
                 y = minY;
                 w = maxX - minX;
                 h = maxY - minY;
             }
+        }
 
         /// <summary>
         /// 命中测试, 当插槽全透明或者处于禁用或者骨骼处于未激活则无法命中