A currency is required message prompt

On entity form a currency type field is placed. When record is opened and some number value is added in it, I got following error message.

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Message from webpage
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A currency is required if a value exists in a money field. Select a currency and try again.
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OK  
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Resolution:

Go to File -> Option. Under General Tab go to option "select a default currency" and then click on "Currency" lookup and specify currency to use.