Exception raised in read-only mode when reading some cells
*Created originally on Bitbucket by [CharlieC](https://bitbucket.org/%7B32d660d5-f934-4ce5-a7b0-52750378fae1%7D/)* openpyxl will raise an exception when trying to read a cell from a worksheet where there is no relevant row in the source file. ie. ws['A60'] for the following source. `ws.iter_rows()` is fine. ``` #!xml <row r="59" spans="1:14" x14ac:dyDescent="0.25"> <c r="A59" t="s"> <v>99</v> </c> </row> <row r="61" spans="1:14" x14ac:dyDescent="0.25"> <c r="A61" t="s"> <v>94</v> </c> </row> ```
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