NSDictionary objectForKey: Crash.

https://www.icloud.com/iclouddrive/0LhunzDSrXWF6qO5fmuyor0yQ#image_(6)

    NSDictionary *description = @{@"a": (self.a ? : @"(null)"),
                                  @"b": [self stringWithState:self.state],
                                  @"c": (self.c ? : @"(null)"),
                                  @"d": (self.product ? self.product.description : @"(null)"),
                                  @"e": (self.e ? : @"(null)"),
                                  @"f": ((self.f && self.f.length > 10) ? [self.f substringToIndex:10] : @"(null)"),
                                  @"g": (self.g ? : @"(null)"),
                                  @"h": (self.h ? : @{}),
                                  @"i": (self.i ? : @"(null)"),
                                  @"j": ((self.j && self.j.length > 20) ? [self.j substringToIndex:20] : @"(null)"),
                                  @"k": (self.k ? : @{}),
                                  @"l": (self.l ? : @"(null)"),
                                  @"m": (self.m ? : @{}),
                                  @"n": (self.n ? : @{})
                                  };
    return [description description];

I use it in the code form above.

By the way, there have been reports of a crash occurring in certain situations.

I can't figure out the cause, so I ask for help.

What should I check?