Fixed the following issues for the new query tool:

1) Failed to fetch query history error sometimes.
 2) In copy paste row, if a copied row has [null], then those are pasted as an empty string.
 3) When Data output is empty, show an empty grid.
 4) Schema diff generates a script button resulting in an empty window. Fixes #7306.
 5) Detach the DataOutput panel > Try editing text cell > Text editor is hidden behind the data output panel

refs #6131

web/pgadmin/static/js/SchemaView/index.jsx

@@ -734,12 +734,12 @@ function SchemaDialogView({
               onClose={onErrClose} />
           </Box>
           {showFooter && <Box className={classes.footer}>
-            {useMemo(()=><Box>
+            {useMemo(()=>((!props.disableSqlHelp || !props.disableDialogHelp) && <Box>
               <PgIconButton data-test="sql-help" onClick={()=>props.onHelp(true, isNew)} icon={<InfoIcon />}
                 disabled={props.disableSqlHelp} className={classes.buttonMargin} title="SQL help for this object type."/>
               <PgIconButton data-test="dialog-help" onClick={()=>props.onHelp(false, isNew)} icon={<HelpIcon />} title="Help for this dialog."
                 disabled={props.disableDialogHelp}/>
-            </Box>, [])}
+            </Box>), [])}
             <Box marginLeft="auto">
               <DefaultButton data-test="Close" onClick={props.onClose} startIcon={<CloseIcon />} className={classes.buttonMargin}>
                 {gettext('Close')}

web/pgadmin/static/js/helpers/Layout.jsx

@@ -40,7 +40,6 @@ const useStyles = makeStyles((theme)=>({
       border: 'none',
       '&.dragging': {
         opacity: 0.6,
-        pointerEvents: 'visible',
       },
       '& .dock':  {
         borderRadius: 'inherit',
@@ -49,6 +48,7 @@ const useStyles = makeStyles((theme)=>({
         borderRadius: theme.shape.borderRadius,
         '&.dock-panel.dragging': {
           opacity: 1,
+          pointerEvents: 'visible',
         },
         '& .dock-ink-bar': {
           height: '0px',

web/pgadmin/static/scss/_codemirror.overrides.scss

@@ -211,5 +211,6 @@
   background-color: $sql-editor-disable-bg !important;
 }
 
-
-
+.sql-editor-mark {
+  border-bottom: 2px dotted red;
+}