block – “Assertion failed!” When trying to download a Bitcoin wallet

When I try to load my Bitcoin wallet, I get the message “Assertion Failed!” Window: The window displays:

Assertion failed! Program: C:\Program Files\Bitcoin\bitcoin-qt.exe File: Validation.cpp Line: 2974 Expression: !setBlockIndexCandidates.empty()

For more information about how your program can cause an assertion failure, see the Visual C++ documentation on assertions. (Press Retry to debug the application. You must enable JIT.)

I really appreciate your help debugging this issue.