Add try-catch to VersionFiltering (#939)

Author: SimunKaracic

instrumentation/kamon-akka-http/src/main/scala/kamon/instrumentation/akka/http/VersionFiltering.scala

@@ -2,7 +2,17 @@ package kamon.instrumentation.akka.http
 
 trait VersionFiltering {
   def onAkkaHttp(version: String)(block: => Unit): Unit = {
-    if(akka.http.Version.current.startsWith(version))
+    val akkaHttpVersion = getVersion
+
+    if (akkaHttpVersion.exists(_.startsWith(version)))
       block
   }
+
+  private def getVersion: Option[String] = {
+    try {
+      Option(akka.http.Version.current)
+    } catch {
+      case _: Throwable => None
+    }
+  }
 }