QmlProfiler: Avoid showing "NaNb" as memory in flame graph details

Change-Id: Ic06885d6c898036efba9b11beb13209351b2629a
Reviewed-by: Milian Wolff <milian.wolff@kdab.com>

src/plugins/qmlprofiler/qml/QmlProfilerFlameGraphView.qml

@@ -199,6 +199,9 @@ ScrollView {
                     }
 
                     function printMemory(a) {
+                        if (a === 0)
+                            return "0b";
+
                         var units = ["b", "kb", "Mb", "Gb"];
                         var div = 1;
                         for (var i = 0; i < units.length; ++i, div *= 1024) {