Cherry-picking WordPress 5.3 RC2 bug fixes (#18046)

Author: youknowriad

packages/block-library/src/columns/editor.scss

@@ -43,7 +43,14 @@
 		> [data-type="core/column"] > .editor-block-list__block-edit .block-core-columns {
 			display: flex;
 			flex-direction: column;
-			flex: 1 0 auto;
+
+			// This flex rule fixes an issue in IE11.
+			flex: 1 1 auto;
+
+			// IE11 does not support `position: sticky`, so we use it here to serve correct Flex rules to modern browsers.
+			@supports (position: sticky) {
+				flex: 1;
+			}
 		}
 
 		// Adjust the individual column block.

packages/media-utils/src/components/media-upload/index.js

@@ -125,9 +125,6 @@ class MediaUpload extends Component {
 		} else {
 			const frameConfig = {
 				title,
-				button: {
-					text: __( 'Select' ),
-				},
 				multiple,
 			};
 			if ( !! allowedTypes ) {

packages/url/src/index.js

@@ -360,6 +360,10 @@ export function removeQueryArgs( url, ...args ) {
  * @return {string} The updated URL.
  */
 export function prependHTTP( url ) {
+	if ( ! url ) {
+		return url;
+	}
+
 	url = url.trim();
 	if ( ! USABLE_HREF_REGEXP.test( url ) && ! EMAIL_REGEXP.test( url ) ) {
 		return 'http://' + url;