catch exceptions thrown at adding a new column to exceptions table

app/src/main/kotlin/com/simplemobiletools/calendar/helpers/DBHelper.kt

@@ -139,7 +139,10 @@ class DBHelper private constructor(val context: Context) : SQLiteOpenHelper(cont
                 createExceptionsTable(db)
             } catch (ignored: SQLiteException) {
             }
+            try {
                 db.execSQL("ALTER TABLE $EXCEPTIONS_TABLE_NAME ADD COLUMN $COL_CHILD_EVENT_ID INTEGER NOT NULL DEFAULT 0")
+            } catch (ignored: SQLiteException) {
+            }
         }
     }