fix: add null content-type header check to traces and metrics endpoints

Signed-off-by: Tim Birkett <109664963+portswigger-tim@users.noreply.github.com>

plugins/in_opentelemetry/opentelemetry_prot.c

@@ -2175,6 +2175,12 @@ static int process_payload_metrics_ng(struct flb_opentelemetry *ctx,
 
     offset = 0;
 
+    if (request->content_type == NULL) {
+        flb_error("[otel] content type missing");
+
+        return -1;
+    }
+
     if (strcasecmp(request->content_type, "application/grpc") == 0) {
         if (cfl_sds_len(request->body) < 5) {
             return -1;
@@ -2221,6 +2227,12 @@ static int process_payload_traces_proto_ng(struct flb_opentelemetry *ctx,
 
     offset = 0;
 
+    if (request->content_type == NULL) {
+        flb_error("[otel] content type missing");
+
+        return -1;
+    }
+
     if (strcasecmp(request->content_type, "application/grpc") == 0) {
         if (cfl_sds_len(request->body) < 5) {
             return -1;