Do not render header if not passed in

Author: jperals

src/split-panel/implementation.tsx

@@ -103,13 +103,15 @@ export function SplitPanelImplementation({
   const wrappedHeader = (
     <div className={clsx(styles.header, isToolbar && styles['with-toolbar'])} style={appLayoutMaxWidth}>
       <div className={styles['header-content']}>
-        <div className={clsx(styles['header-main-row'], showDescription && styles['with-description'])}>
+        <div className={styles['header-main-row']}>
           <div className={styles['header-start']}>
             {headerBefore && <span className={styles['header-before-slot']}>{headerBefore}</span>}
             <div className={styles['header-text-and-info']}>
-              <h2 className={clsx(styles['header-text'], testUtilStyles['header-text'])} id={panelHeaderId}>
-                {header}
-              </h2>
+              {header && (
+                <h2 className={clsx(styles['header-text'], testUtilStyles['header-text'])} id={panelHeaderId}>
+                  {header}
+                </h2>
+              )}
               {headerInfo && <span className={styles['header-info-slot']}>{headerInfo}</span>}
             </div>
           </div>

src/split-panel/styles.scss

@@ -240,13 +240,6 @@ $app-layout-drawer-width: calc(#{awsui.$space-layout-toggle-diameter} + 2 * #{aw
   &-main-row,
   &-text-and-info {
     display: flex;
-    flex-grow: 1;
-  }
-
-  &-content,
-  &-start,
-  &-text-and-info {
-    flex-grow: 1;
   }
 
   &-main-row,
@@ -256,11 +249,6 @@ $app-layout-drawer-width: calc(#{awsui.$space-layout-toggle-diameter} + 2 * #{aw
     column-gap: awsui.$space-scaled-xs;
     row-gap: awsui.$space-scaled-xxs;
   }
-
-  &-content {
-    align-items: flex-start;
-  }
-
   &-main-row {
     flex: auto;
     flex-direction: row;
@@ -270,6 +258,11 @@ $app-layout-drawer-width: calc(#{awsui.$space-layout-toggle-diameter} + 2 * #{aw
 
   &-start {
     align-items: center;
+    flex-grow: 1;
+  }
+
+  &-content {
+    align-items: flex-start;
   }
 
   &-text-and-info {