fix(withWebComponent): filter out empty strings

Empty strings, e.g. from default props might lead to unintended behavior, e.g. showing a popover header although it was not defined.

Author: MarcusNotheis

packages/main/src/components/ActionSheet/__snapshots__/ActionSheet.test.tsx.snap

@@ -3,9 +3,7 @@
 exports[`ActionSheet Render without Crashing 1`] = `
 <ui5-responsive-popover
   class="ActionSheet-actionSheet-0 myCustomClass"
-  header-text=""
   horizontal-align="Center"
-  initial-focus=""
   placement-type="Right"
   vertical-align="Center"
 >
@@ -19,14 +17,12 @@ exports[`ActionSheet Render without Crashing 1`] = `
   <ui5-button
     data-is-action-sheet-button=""
     design="Transparent"
-    icon=""
   >
     Reject
   </ui5-button>
   <ui5-button
     data-is-action-sheet-button=""
     design="Transparent"
-    icon=""
   >
     This is my super long text!
   </ui5-button>
@@ -36,16 +32,13 @@ exports[`ActionSheet Render without Crashing 1`] = `
 exports[`ActionSheet does not crash with other component 1`] = `
 <ui5-responsive-popover
   class="ActionSheet-actionSheet-0"
-  header-text=""
   horizontal-align="Center"
-  initial-focus=""
   placement-type="Right"
   vertical-align="Center"
 >
   <ui5-label
     data-is-action-sheet-button=""
     design="Transparent"
-    for=""
   >
     I should not crash
   </ui5-label>