fix(md-chips placeholder): correct placeholder/secondary logic
fix(md-chips placeholder): correct placeholder/secondary logic

The logic test deciding when to show the secondary placeholder was backwards, causing the secondary placeholder to be shown when no chips were present.

Fixes github issues #2770 and #4476.

Closes #6535

2947721120/angular-material,JonFerrera/material,graingert/material,j3ski/material,acoreyj/material,DevVersion/material,welkinhealth/material,robertmesserle/material,programmist/material,pwistbac/material,hayloft/material,Frank3K/material,DerekLouie/material,dmitriz/material,dmitriz/material,miguelcobain/material,HarrisCorp/material,gkalpak/material,crisbeto/material,Frank3K/material,welkinhealth/material,jelbourn/material,j3ski/material,gmoothart/material,DerekLouie/material,colinskow/material,hayloft/material,bluebirdtech/material,JonFerrera/material,graingert/material,Frank3K/material,clshortfuse/material,hayloft/material,ErinCoughlan/material,JonFerrera/material,HipsterZipster/material,colinskow/material,ErinCoughlan/material,david-gang/material,hodeyp/material,hodeyp/material,crisbeto/material,robertmesserle/material,epelc/material,angular/material,bluebirdtech/material,clshortfuse/material,welkinhealth/material,vertazzar/material,miguelcobain/material,gmoothart/material,DerekLouie/material,ErinCoughlan/material,oostmeijer/material,HipsterZipster/material,marekmicek/material,david-gang/material,DevVersion/material,colinskow/material,daniel-nagy/material,epelc/material,robertmesserle/material,imjoeco/material,clshortfuse/material,programmist/material,kamilkisiela/material,epelc/material,imjoeco/material,SamDLT/material,HarrisCorp/material,DevVersion/material,clshortfuse/material,david-gang/material,programmist/material,daniel-nagy/material,hodeyp/material,marekmicek/material,j3ski/material,acoreyj/material,DerekLouie/material,welkinhealth/material,2947721120/angular-material,oostmeijer/material,jadjoubran/material,ilovett/material,ServiceManagementGroup/material,marekmicek/material,graingert/material,DevVersion/material,gmoothart/material,miguelcobain/material,profoundry-us/material,pwistbac/material,hayloft/material,Frank3K/material,robertmesserle/material,gkalpak/material,ServiceManagementGroup/material,miguelcobain/material,2947721120/angular-material,acoreyj/material,profoundry-us/material,gkalpak/material,jadjoubran/material,jelbourn/material,jelbourn/material,marekmicek/material,jelbourn/material,vertazzar/material,ilovett/material,vertazzar/material,gkalpak/material,acoreyj/material,angular/material,2947721120/angular-material,david-gang/material,daniel-nagy/material,HipsterZipster/material,programmist/material,jadjoubran/material,Splaktar/material,daniel-nagy/material,profoundry-us/material,gmoothart/material,HarrisCorp/material,bluebirdtech/material,imjoeco/material,bluebirdtech/material,profoundry-us/material,angular/material,Splaktar/material,jadjoubran/material,j3ski/material,dmitriz/material,angular/material,graingert/material,dmitriz/material,crisbeto/material,oostmeijer/material,kamilkisiela/material,vertazzar/material,crisbeto/material,ilovett/material,colinskow/material,oostmeijer/material,HipsterZipster/material,ServiceManagementGroup/material,JonFerrera/material,pwistbac/material,SamDLT/material,Splaktar/material,ErinCoughlan/material,ServiceManagementGroup/material,imjoeco/material,HarrisCorp/material,kamilkisiela/material,SamDLT/material,pwistbac/material,SamDLT/material,hodeyp/material,epelc/material,kamilkisiela/material,Splaktar/material,ilovett/material