Verify that reference.name is not nil

Author: jspahrsummers

Classes/GTReflog.m

@@ -32,6 +32,7 @@ - (void)dealloc {
 
 - (id)initWithReference:(GTReference *)reference {
 	NSParameterAssert(reference != nil);
+	NSParameterAssert(reference.name != nil);
 
 	self = [super init];
 	if (self == nil) return nil;