Handle non-integer stack trace line numbers in .NET

The .NET bindings assumed that the stack trace elements in the wire
protocol would have line numbers that were integers, as specified in the
OSS-dialect of the protocol. This is not necessarily the case, and we need
to be a little more forgiving.

Fixes issue #2774.

dotnet/src/webdriver/Remote/StackTraceElement.cs

@@ -60,7 +60,11 @@ public StackTraceElement(Dictionary<string, object> elementAttributes)
 
                 if (elementAttributes.ContainsKey("lineNumber"))
                 {
-                    this.lineNumber = Convert.ToInt32(elementAttributes["lineNumber"], CultureInfo.InvariantCulture);
+                    int line = 0;
+                    if (int.TryParse(elementAttributes["lineNumber"].ToString(), out line))
+                    {
+                        this.lineNumber = line;
+                    }
                 }
 
                 if (elementAttributes.ContainsKey("fileName") && elementAttributes["fileName"] != null)