Fix Qt 5.7 build

Author: iamantony

.travis.yml

@@ -35,7 +35,7 @@ install:
   - if [ "$QT_BASE" = "54" ]; then sudo apt-get install -qq qt54base; source /opt/qt54/bin/qt54-env.sh; fi
   - if [ "$QT_BASE" = "55" ]; then sudo apt-get install -qq qt55base; source /opt/qt55/bin/qt55-env.sh; fi
   - if [ "$QT_BASE" = "56" ]; then sudo apt-get install -qq qt56base; source /opt/qt56/bin/qt56-env.sh; fi
-  - if [ "$QT_BASE" = "57" ]; then sudo apt-get install -qq qt56base; source /opt/qt57/bin/qt57-env.sh; fi
+  - if [ "$QT_BASE" = "57" ]; then sudo apt-get install -qq qt57base; source /opt/qt57/bin/qt57-env.sh; fi
 
 script:
   - qmake -r