Fix crash in grpc_errorFromStatusCode

src/objective-c/GRPCClient/private/NSError+GRPC.h

@@ -25,6 +25,6 @@
  * and whose domain is |kGRPCErrorDomain|.
  */
 + (instancetype)grpc_errorFromStatusCode:(grpc_status_code)statusCode
-                                 details:(char *)details
+                                 details:(const char *)details
                              errorString:(const char *)errorString;
 @end

src/objective-c/GRPCClient/private/NSError+GRPC.m

@@ -24,18 +24,20 @@ NSString *const kGRPCErrorDomain = @"io.grpc";
 
 @implementation NSError (GRPC)
 + (instancetype)grpc_errorFromStatusCode:(grpc_status_code)statusCode
-                                 details:(char *)details
+                                 details:(const char *)details
                              errorString:(const char *)errorString {
   if (statusCode == GRPC_STATUS_OK) {
     return nil;
   }
-  NSString *message = [NSString stringWithCString:details encoding:NSUTF8StringEncoding];
-  NSString *debugMessage = [NSString stringWithCString:errorString encoding:NSUTF8StringEncoding];
+  NSMutableDictionary *userInfo = [NSMutableDictionary dictionary];
+  if (details) {
+    userInfo[NSLocalizedDescriptionKey] = [NSString stringWithCString:details encoding:NSUTF8StringEncoding];
+  }
+  if (errorString) {
+    userInfo[NSDebugDescriptionErrorKey] = [NSString stringWithCString:errorString encoding:NSUTF8StringEncoding];
+  }
   return [NSError errorWithDomain:kGRPCErrorDomain
                              code:statusCode
-                         userInfo:@{
-                           NSLocalizedDescriptionKey : message,
-                           NSDebugDescriptionErrorKey : debugMessage
-                         }];
+                         userInfo:userInfo];
 }
 @end