Made the code safer by removing the force cast and modified the heade…

…r dictonary building to use reduce(into:) so that the overall code is more idionatic Swift

Sources/Bugsnag/BugsnagReporter.swift

@@ -103,15 +103,14 @@ extension BugsnagReporter {
                 eventRequestBody = nil
             }
 
-            var headerDict: [String : Any] = request.headers.reduce([:], { result, value in
-                var copy = result
-                copy[value.0] = value.1
-                return copy
-            })
+            var headerDict: [String : Any] = request.headers.reduce(into: [:]) { result, value in
+                result[value.0] = value.1
+            }
             strip(keys: configuration.keyFilters, from: &headerDict)
 
-            let filteredHeaders: [(String, String)] = headerDict.map {
-                k, v in (k, v as! String)
+            let filteredHeaders: [(String, String)] = headerDict.compactMap { k, v in
+                guard let value = v as? String else { return nil }
+                return (k, value)
             }
 
             eventRequest = .init(