Fix missing value data in graph (#2230)

* fix missing value data

---------

Co-authored-by: CaCO3 <caco@ruinelli.ch>

sd-card/html/graph.html

@@ -50,39 +50,19 @@
 
                             /* Catch empty fields */
                             if (value == "" || isNaN(value)) {
-                                if (traceValue.y.length > 0) {
-                                    value = traceValue.y[traceValue.y.length-1];
-                                }
-                                else {
-                                    value = 0;
-                                }
+                                value = NaN;
                             }
 
                             if (preValue == "" || isNaN(preValue)) {
-                                if (tracePreValue.y.length > 0) {
-                                    preValue = tracePreValue.y[tracePreValue.y.length-1];
-                                }
-                                else {
-                                    preValue = 0;
-                                }
+                                preValue = NaN;
                             }
 
                             if (changeRate == "" || isNaN(changeRate)) {
-                                if (traceChangeRate.y.length > 0) {
-                                    changeRate = traceChangeRate.y[traceChangeRate.y.length-1];
-                                }
-                                else {
-                                    changeRate = 0;
-                                }
+                                changeRate = NaN;
                             }
 
                             if (changeAbsolute == "" || isNaN(changeAbsolute)) {
-                                if (traceChangeAbsolute.y.length > 0) {
-                                    changeAbsolute = traceChangeAbsolute.y[traceChangeAbsolute.y.length-1];
-                                }
-                                else {
-                                    changeAbsolute = 0;
-                                }
+                                changeAbsolute = NaN;
                             }
 
                             traceValue.y.push(value);
@@ -104,6 +84,8 @@
                 var offsetValue = traceValue.y[0];
                 var offsetPreValue = tracePreValue.y[0];
 
+                traceValue.connectgaps = true;
+
                 if (showRrelativeValues) {
                     traceValue.y.forEach(function(part, index, arr) {
                         arr[index] = arr[index] - offsetValue;