Never connect null values in sample dashboard

When null values are connected, it can be hard to determine when a
sensor stopped reporting or when a restart occurred.

assets/dashboards/ohm-prometheus.json

@@ -1380,7 +1380,7 @@
               "type": "linear"
             },
             "showPoints": "never",
-            "spanNulls": true,
+            "spanNulls": false,
             "stacking": {
               "group": "A",
               "mode": "normal"
@@ -1473,7 +1473,7 @@
               "type": "linear"
             },
             "showPoints": "never",
-            "spanNulls": true,
+            "spanNulls": false,
             "stacking": {
               "group": "A",
               "mode": "none"
@@ -1569,7 +1569,7 @@
               "type": "linear"
             },
             "showPoints": "never",
-            "spanNulls": true,
+            "spanNulls": false,
             "stacking": {
               "group": "A",
               "mode": "none"
@@ -1669,7 +1669,7 @@
               "type": "linear"
             },
             "showPoints": "never",
-            "spanNulls": true,
+            "spanNulls": false,
             "stacking": {
               "group": "A",
               "mode": "none"
@@ -1765,7 +1765,7 @@
               "type": "linear"
             },
             "showPoints": "never",
-            "spanNulls": true,
+            "spanNulls": false,
             "stacking": {
               "group": "A",
               "mode": "none"
@@ -1876,7 +1876,7 @@
               "type": "linear"
             },
             "showPoints": "never",
-            "spanNulls": true,
+            "spanNulls": false,
             "stacking": {
               "group": "A",
               "mode": "none"
@@ -1979,7 +1979,7 @@
               "type": "linear"
             },
             "showPoints": "never",
-            "spanNulls": true,
+            "spanNulls": false,
             "stacking": {
               "group": "A",
               "mode": "none"
@@ -2085,7 +2085,7 @@
               "type": "linear"
             },
             "showPoints": "never",
-            "spanNulls": true,
+            "spanNulls": false,
             "stacking": {
               "group": "A",
               "mode": "none"
@@ -2192,7 +2192,7 @@
               "type": "linear"
             },
             "showPoints": "never",
-            "spanNulls": true,
+            "spanNulls": false,
             "stacking": {
               "group": "A",
               "mode": "none"
@@ -2287,7 +2287,7 @@
               "type": "linear"
             },
             "showPoints": "never",
-            "spanNulls": true,
+            "spanNulls": false,
             "stacking": {
               "group": "A",
               "mode": "none"
@@ -2382,7 +2382,7 @@
               "type": "linear"
             },
             "showPoints": "never",
-            "spanNulls": true,
+            "spanNulls": false,
             "stacking": {
               "group": "A",
               "mode": "none"
@@ -2506,7 +2506,7 @@
               "type": "linear"
             },
             "showPoints": "never",
-            "spanNulls": true,
+            "spanNulls": false,
             "stacking": {
               "group": "A",
               "mode": "none"
@@ -3387,7 +3387,7 @@
               "type": "linear"
             },
             "showPoints": "never",
-            "spanNulls": true,
+            "spanNulls": false,
             "stacking": {
               "group": "A",
               "mode": "none"
@@ -3478,7 +3478,7 @@
               "type": "linear"
             },
             "showPoints": "never",
-            "spanNulls": true,
+            "spanNulls": false,
             "stacking": {
               "group": "A",
               "mode": "none"
@@ -3602,7 +3602,7 @@
               "type": "linear"
             },
             "showPoints": "never",
-            "spanNulls": true,
+            "spanNulls": false,
             "stacking": {
               "group": "A",
               "mode": "none"
@@ -3868,7 +3868,7 @@
               "type": "linear"
             },
             "showPoints": "never",
-            "spanNulls": true,
+            "spanNulls": false,
             "stacking": {
               "group": "A",
               "mode": "none"
@@ -4076,5 +4076,5 @@
   "timezone": "",
   "title": "Ohm Windows Desktop",
   "uid": "EEQD4wv7z",
-  "version": 39
+  "version": 40
 }