add an extra assert to check memory bounds
add an extra assert to check memory bounds

-> will remove a static-analysis warning about unused value.
addresses issue #138

Change-Id: I8ba4bf71a41e32759da41907aab73108dd230bc4

jiehu5114/libwebp,matanbs/webm.libwebp,keane83/BLE_IM,zofuthan/libwebp,webmproject/libwebp,webmproject/libwebp,rxl194/libwebp,PKRoma/libwebp,reimaginemedia/webm.libwebp,iniwf/webm.libwebp,redengineer/libwebp,Maria1099/webm.libwebp,imazen/libwebp,abwiz0086/webm.libwebp,iniwf/webm.libwebp,jacklicn/libwebp,matanbs/webm.libwebp,abwiz0086/webm.libwebp,yohunl/libwebp,Acidburn0zzz/webm.libwebp,ya7lelkom/libwebp,yohunl/libwebp,comoyo/gonzo-libwebp,ericmckean/webm.libwebp,gshORTON/webm.libwebp,ya7lelkom/libwebp,redengineer/libwebp,yohunl/libwebp,dumganhar/libwebp,Tekserve/libwebp,abwiz0086/webm.libwebp,rxl194/libwebp,Suvarna1488/webm.libwebp,ya7lelkom/libwebp,abwiz0086/webm.libwebp,kalli123/webm.libwebp,PKRoma/libwebp,Aexyn/libwebp,iniwf/webm.libwebp,kleopatra999/webm.libwebp,appunite/libwebp,Suvarna1488/webm.libwebp,iniwf/webm.libwebp,gshORTON/webm.libwebp,kalli123/webm.libwebp,Acidburn0zzz/webm.libwebp,kalli123/webm.libwebp,zofuthan/libwebp,rxl194/libwebp,jacklicn/libwebp,kim42083/webm.libwebp,comoyo/gonzo-libwebp,cysp/libwebp,keane83/BLE_IM,Maria1099/webm.libwebp,Aexyn/libwebp,Acidburn0zzz/webm.libwebp,keane83/BLE_IM,kalli123/webm.libwebp,zofuthan/libwebp,appunite/libwebp,yohunl/libwebp,reimaginemedia/webm.libwebp,Aexyn/libwebp,imazen/libwebp,redengineer/libwebp,ericmckean/webm.libwebp,ya7lelkom/libwebp,ericmckean/webm.libwebp,reimaginemedia/webm.libwebp,PKRoma/libwebp,webmproject/libwebp,dumganhar/libwebp,comoyo/gonzo-libwebp,kleopatra999/webm.libwebp,cysp/libwebp,cysp/libwebp,comoyo/gonzo-libwebp,kim42083/webm.libwebp,redengineer/libwebp,Maria1099/webm.libwebp,PKRoma/libwebp,ttyangf/libwebp,Maria1099/webm.libwebp,ttyangf/libwebp,kleopatra999/webm.libwebp,altogother/webm.libwebp,altogother/webm.libwebp,ericmckean/webm.libwebp,ya7lelkom/libwebp,keane83/BLE_IM,reimaginemedia/webm.libwebp,jacklicn/libwebp,rxl194/libwebp,webmproject/libwebp,jiehu5114/libwebp,Distrotech/libwebp,keane83/BLE_IM,Maria1099/webm.libwebp,ttyangf/libwebp,kleopatra999/webm.libwebp,imazen/libwebp,jacklicn/libwebp,cysp/libwebp,zofuthan/libwebp,appunite/libwebp,jacklicn/libwebp,altogother/webm.libwebp,comoyo/gonzo-libwebp,jiehu5114/libwebp,Distrotech/libwebp,gshORTON/webm.libwebp,altogother/webm.libwebp,zofuthan/libwebp,ericmckean/webm.libwebp,Suvarna1488/webm.libwebp,kim42083/webm.libwebp,matanbs/webm.libwebp,altogother/webm.libwebp,redengineer/libwebp,PKRoma/libwebp,ttyangf/libwebp,kalli123/webm.libwebp,appunite/libwebp,jiehu5114/libwebp,reimaginemedia/webm.libwebp,imazen/libwebp,webmproject/libwebp,Tekserve/libwebp,kim42083/webm.libwebp,Suvarna1488/webm.libwebp,appunite/libwebp,dumganhar/libwebp,Aexyn/libwebp,kleopatra999/webm.libwebp,yohunl/libwebp,Tekserve/libwebp,rxl194/libwebp,jiehu5114/libwebp,Aexyn/libwebp,imazen/libwebp,gshORTON/webm.libwebp,Tekserve/libwebp,matanbs/webm.libwebp,Distrotech/libwebp,Suvarna1488/webm.libwebp,comoyo/gonzo-libwebp,ttyangf/libwebp,iniwf/webm.libwebp,appunite/libwebp,comoyo/gonzo-libwebp,Acidburn0zzz/webm.libwebp,matanbs/webm.libwebp,Acidburn0zzz/webm.libwebp,abwiz0086/webm.libwebp,gshORTON/webm.libwebp,PKRoma/libwebp,kim42083/webm.libwebp