REPORT-59440 【主题切换】合并单元格以后，单元格样式都变成了自定义

【问题原因】
合并时新建单元格需要在设计器模块中处理，已获取当前正在编辑模版的主题数据来设置样式

【改动思路】
同标题

designer-realize/src/main/java/com/fr/grid/selection/CellSelection.java

@@ -383,8 +383,27 @@ public class CellSelection extends Selection {
                 return false;
             }
         }
-
-        ec.merge(row, row + rowSpan - 1, column, column + columnSpan - 1);
+        int rowStartIndex = row;
+        int rowEndIndex = row + rowSpan - 1;
+        int columnStartIndex = column;
+        int columnEndIndex = column + columnSpan - 1;
+
+        // 合并已有单元格，还是新建单元格
+        boolean hasCellElement = false;
+        for (int ri = rowStartIndex; ri <= rowEndIndex; ri++) {
+            for (int ci = columnStartIndex; ci <= columnEndIndex; ci++) {
+                CellElement ce = ec.getCellElement(ci, ri);
+                if (ce != null) {
+                    hasCellElement = true;
+                    break;
+                }
+            }
+        }
+        if (hasCellElement) {
+            ec.merge(row, row + rowSpan - 1, column, column + columnSpan - 1);
+        } else {
+            ec.addCellElement(DefaultThemedTemplateCellElementCase.createInstance(column, row, columnSpan, rowSpan, null), true);
+        }
 
         return true;
     }