Update key's to use empty string to prevent errors when null header bug is present in framework

Author: webdevnerdstuff

src/documentation/components/examples/ClientTable.vue

@@ -94,7 +94,7 @@ const headers = {
 	comments: [
 		{
 			align: 'start',
-			key: null,
+			key: '',
 			title: '',
 			width: 110,
 		},
@@ -184,7 +184,7 @@ const footers = {
 	comments: [
 		{
 			align: 'start',
-			key: null,
+			key: '',
 			title: '',
 			width: 100,
 		},

src/documentation/components/examples/ServerTable.vue

@@ -93,7 +93,7 @@ const headers = {
 	comments: [
 		{
 			align: 'start',
-			key: null,
+			key: '',
 			title: '',
 			width: 110,
 		},
@@ -183,7 +183,7 @@ const footers = {
 	comments: [
 		{
 			align: 'start',
-			key: null,
+			key: '',
 			title: '',
 			width: 100,
 		},