Fix overwriting existing line height style when none has been set in …

…CoBlocks (#1526)

* Don't force style to null when typography setting is undefined

Fixes #1500

* Update contributor username

CONTRIBUTORS.md

@@ -30,7 +30,7 @@ This list is manually curated to include valuable contributions by volunteers th
 | @mahdiyazdani     | @mahdiyazdani          |
 | @nicolad          | @vadimnicolai          |
 | @obenland         | @obenland              |
-| @p-jackson        |                        |
+| @p-jackson        | @philipmjackson        |
 | @passatgt         | @passatgt              |
 | @ramiy            | @ramiy                 |
 | @Reinpal          |                        |

src/extensions/typography/apply-style.js

@@ -1,19 +1,12 @@
-function applyStyle( attributes, name ) {
-	const {
-		fontFamily,
-		lineHeight,
-		letterSpacing,
-		fontWeight,
-		textTransform,
-	} = attributes;
+/**
+ * External dependencies
+ */
+import pickBy from 'lodash/pickby';
+
+const styleAttributes = [ 'fontFamily', 'lineHeight', 'letterSpacing', 'fontWeight', 'textTransform' ];
 
-	const style = {
-		lineHeight: lineHeight || null,
-		fontFamily: fontFamily || null,
-		fontWeight: fontWeight || null,
-		textTransform: textTransform || null,
-		letterSpacing: letterSpacing || null,
-	};
+function applyStyle( attributes, name ) {
+	const style = pickBy( attributes, ( value, key ) => !! value && styleAttributes.includes( key ) );
 
 	if ( typeof attributes.customFontSize !== 'undefined' ) {
 		style.fontSize = attributes.customFontSize + 'px';