convert to guard statements for readability

SignalServiceKit/src/Contacts/PhoneNumber.m

@@ -324,18 +324,24 @@ static NSString *const RPDefaultsKeyPhoneNumberCanonical = @"RPDefaultsKeyPhoneN
 
     // Order matters; better results should appear first so prefer
     // matches with the same country code as this client's phone number.
-    OWSAssertDebug(clientPhoneNumber.length > 0);
+    if (clientPhoneNumber.length == 0) {
-    if (clientPhoneNumber.length > 0) {
+        OWSFailDebug(@"clientPhoneNumber had unexpected length");
+        return result;
+    }
+
     // Note that NBPhoneNumber uses "country code" to refer to what we call a
     // "calling code" (i.e. 44 in +44123123).  Within SSK we use "country code"
     // (and sometimes "region code") to refer to a country's ISO 2-letter code
     // (ISO 3166-1 alpha-2).
     NSNumber *callingCodeForLocalNumber = [[PhoneNumber phoneNumberFromE164:clientPhoneNumber] getCountryCode];
-        if (callingCodeForLocalNumber != nil) {
+    if (callingCodeForLocalNumber == nil) {
+        OWSFailDebug(@"callingCodeForLocalNumber was unexpectedly nil");
+        return result;
+    }
+
     NSString *callingCodePrefix = [NSString stringWithFormat:@"+%@", callingCodeForLocalNumber];
 
-            tryParsingWithCountryCode(
+    tryParsingWithCountryCode([callingCodePrefix stringByAppendingString:sanitizedString], [self defaultCountryCode]);
-                [callingCodePrefix stringByAppendingString:sanitizedString], [self defaultCountryCode]);
 
     // Try to determine what the country code is for the local phone number
     // and also try parsing the phone number using that country code if it
@@ -347,10 +353,7 @@ static NSString *const RPDefaultsKeyPhoneNumberCanonical = @"RPDefaultsKeyPhoneN
     NSString *localCountryCode =
         [PhoneNumberUtil.sharedThreadLocal probableCountryCodeForCallingCode:callingCodePrefix];
     if (localCountryCode && ![localCountryCode isEqualToString:[self defaultCountryCode]]) {
-                tryParsingWithCountryCode(
+        tryParsingWithCountryCode([callingCodePrefix stringByAppendingString:sanitizedString], localCountryCode);
-                    [callingCodePrefix stringByAppendingString:sanitizedString], localCountryCode);
-            }
-        }
     }
 
     return result;