use ternary conditional instead if

lib/src/models/rules/insert.dart

@@ -568,19 +568,17 @@ class PreserveInlineStylesRule extends InsertRule {
       if (prevData.endsWith('\n')) {
         /// If current line is empty get attributes from a prior line
         final currLine = itr.next();
-        if (currLine.data is String) {
-          final currData = currLine.data as String?;
-          if (currData != null && (currData.isEmpty || currData[0] == '\n')) {
-            if (prevData.trimRight().isEmpty) {
-              final back =
-                  DeltaIterator(documentDelta).skip(index - prevData.length);
-              if (back != null && back.data is String) {
-                prev = back;
-              }
+        final currData = currLine.data is String ? currLine.data as String : null;
+        if (currData != null && (currData.isEmpty || currData[0] == '\n')) {
+          if (prevData.trimRight().isEmpty) {
+            final back =
+                DeltaIterator(documentDelta).skip(index - prevData.length);
+            if (back != null && back.data is String) {
+              prev = back;
             }
-          } else {
-            prev = currLine;
           }
+        } else {
+          prev = currLine;
         }
       }
     }