Resolved at https://gerrit.wikimedia.org/r/#change,5212,patchset=1

Platonides brought up an excellent point in code review in regards to an oversight I made when doing:
if ( !empty( $this->mParams['placeholder'] ) ) {

			$attribs['placeholder'] = $this->mParams['placeholder'];
		}

He said:
"What if the placeholder was a 0 ?"

This should probably be handled with isset() rather than !empty().

Better fix with commit fb01ab5dcfc80216f0540f2464c6f7c6c1d51fac, Change-Id: I139abff427d7342fc3283ed3428d0a538331d2b5 (https://gerrit.wikimedia.org/r/#change,5498)