Fix build break.

// FREEBIE

SignalServiceKit/src/Util/DataSource.h

@@ -45,7 +45,7 @@ NS_ASSUME_NONNULL_BEGIN
 
 + (nullable DataSource *)dataSourceWithData:(NSData *)data utiType:(NSString *)utiType;
 
-+ (nullable DataSource *)dataSourceWithOversizeText:(NSString *)text;
++ (nullable DataSource *)dataSourceWithOversizeText:(NSString *_Nullable)text;
 
 + (DataSource *)dataSourceWithSyncMessage:(NSData *)data;
 

SignalServiceKit/src/Util/DataSource.m

@@ -145,10 +145,8 @@ NS_ASSUME_NONNULL_BEGIN
     return [self dataSourceWithData:data fileExtension:fileExtension];
 }
 
-+ (nullable DataSource *)dataSourceWithOversizeText:(NSString *)text
++ (nullable DataSource *)dataSourceWithOversizeText:(NSString *_Nullable)text
 {
-    OWSAssert(text);
-
     if (!text) {
         return nil;
     }