Skip cells that don't have any code in them (microsoft#6644)

Author: rchiodo

src/client/datascience/editor-integration/cellhashprovider.ts

@@ -111,7 +111,7 @@ export class CellHashProvider implements ICellHashProvider, IInteractiveWindowLi
  const lines = splitMultilineString(cell.data.source);
  const stripped = lines.filter(l => !cellMatcher.isCode(l));
 
- if (stripped.length > 0 && stripped.find(s => s.length > 0)) {
+ if (stripped.length > 0 && stripped.find(s => s.trim().length > 0)) {
  // When the user adds new code, we know the execution count is increasing
  this.executionCount += 1;