Tweak Sentry GRPC error processor

It appears the error processor was not able to sanitize some errors
because the `message` did not contain `GRPC::`; that was only present in
the exception `type`. We adjust the processor to handle this
undocumented structure.

lib/gitlab/error_tracking/processor/grpc_error_processor.rb

@@ -24,9 +24,11 @@ module Gitlab
 
           return unless entry.is_a?(Hash)
 
+          exception_type = entry[:type]
           raw_message = entry[:value]
 
-          return unless raw_message.start_with?('GRPC::')
+          return unless exception_type&.start_with?('GRPC::')
+          return unless raw_message.present?
 
           message, debug_str = split_debug_error_string(raw_message)
 

spec/lib/gitlab/error_tracking/processor/grpc_error_processor_spec.rb

@@ -20,7 +20,8 @@ RSpec.describe Gitlab::ErrorTracking::Processor::GrpcErrorProcessor do
           exception: {
             values: [
               {
-                value: "GRPC::DeadlineExceeded: 4:DeadlineExceeded. debug_error_string:{\"hello\":1}"
+                type: "GRPC::DeadlineExceeded",
+                value: "4:DeadlineExceeded. debug_error_string:{\"hello\":1}"
               }
             ]
           },
@@ -43,7 +44,8 @@ RSpec.describe Gitlab::ErrorTracking::Processor::GrpcErrorProcessor do
           exception: {
             values: [
               {
-                value: "GRPC::DeadlineExceeded: 4:DeadlineExceeded."
+                type: "GRPC::DeadlineExceeded",
+                value: "4:DeadlineExceeded."
               }
             ]
           },