ARROW-1770: [GLib] Fix GLib compiler warning
ARROW-1770: [GLib] Fix GLib compiler warning

Author: Phillip Cloud <cpcloud@gmail.com>

Closes #1287 from cpcloud/ARROW-1770 and squashes the following commits:

bb406961 [Phillip Cloud] ARROW-1770: [GLib] Fix GLib compiler warning

yufeldman/arrow,icexelloss/arrow,dremio/arrow,renesugar/arrow,itaiin/arrow,itaiin/arrow,wesm/arrow,majetideepak/arrow,siddharthteotia/arrow,wesm/arrow,icexelloss/arrow,majetideepak/arrow,wesm/arrow,laurentgo/arrow,yufeldman/arrow,cpcloud/arrow,cpcloud/arrow,tebeka/arrow,laurentgo/arrow,cpcloud/arrow,laurentgo/arrow,wagavulin/arrow,cpcloud/arrow,majetideepak/arrow,siddharthteotia/arrow,apache/arrow,laurentgo/arrow,dremio/arrow,wagavulin/arrow,apache/arrow,itaiin/arrow,cpcloud/arrow,apache/arrow,tebeka/arrow,pcmoritz/arrow,kou/arrow,icexelloss/arrow,majetideepak/arrow,majetideepak/arrow,renesugar/arrow,tebeka/arrow,xhochy/arrow,itaiin/arrow,renesugar/arrow,majetideepak/arrow,icexelloss/arrow,apache/arrow,yufeldman/arrow,pcmoritz/arrow,tebeka/arrow,kou/arrow,tebeka/arrow,xhochy/arrow,renesugar/arrow,xhochy/arrow,wesm/arrow,wagavulin/arrow,apache/arrow,dremio/arrow,pcmoritz/arrow,icexelloss/arrow,xhochy/arrow,xhochy/arrow,laurentgo/arrow,wesm/arrow,xhochy/arrow,apache/arrow,laurentgo/arrow,wesm/arrow,itaiin/arrow,kou/arrow,cpcloud/arrow,laurentgo/arrow,icexelloss/arrow,icexelloss/arrow,icexelloss/arrow,xhochy/arrow,kou/arrow,xhochy/arrow,wagavulin/arrow,pcmoritz/arrow,cpcloud/arrow,wesm/arrow,pcmoritz/arrow,wesm/arrow,icexelloss/arrow,pcmoritz/arrow,kou/arrow,apache/arrow,laurentgo/arrow,tebeka/arrow,apache/arrow,itaiin/arrow,dremio/arrow,apache/arrow,apache/arrow,majetideepak/arrow,yufeldman/arrow,renesugar/arrow,wagavulin/arrow,majetideepak/arrow,xhochy/arrow,tebeka/arrow,dremio/arrow,xhochy/arrow,wesm/arrow,laurentgo/arrow,wagavulin/arrow,cpcloud/arrow,majetideepak/arrow,majetideepak/arrow,laurentgo/arrow,majetideepak/arrow,pcmoritz/arrow,wagavulin/arrow,cpcloud/arrow,itaiin/arrow,cpcloud/arrow,kou/arrow,kou/arrow,yufeldman/arrow,apache/arrow,pcmoritz/arrow,icexelloss/arrow,itaiin/arrow,wagavulin/arrow,laurentgo/arrow,renesugar/arrow,pcmoritz/arrow,renesugar/arrow,wesm/arrow,kou/arrow,yufeldman/arrow,dremio/arrow,wesm/arrow,laurentgo/arrow,yufeldman/arrow,icexelloss/arrow,siddharthteotia/arrow,laurentgo/arrow,majetideepak/arrow,dremio/arrow,yufeldman/arrow,tebeka/arrow,renesugar/arrow,majetideepak/arrow,icexelloss/arrow,siddharthteotia/arrow,dremio/arrow,pcmoritz/arrow,apache/arrow,yufeldman/arrow,renesugar/arrow,cpcloud/arrow,yufeldman/arrow,itaiin/arrow,dremio/arrow,dremio/arrow,renesugar/arrow,pcmoritz/arrow,kou/arrow,xhochy/arrow,itaiin/arrow,kou/arrow,siddharthteotia/arrow,xhochy/arrow,pcmoritz/arrow,dremio/arrow,cpcloud/arrow,itaiin/arrow,renesugar/arrow,itaiin/arrow,renesugar/arrow,icexelloss/arrow,laurentgo/arrow,majetideepak/arrow,siddharthteotia/arrow,renesugar/arrow,itaiin/arrow,wesm/arrow,majetideepak/arrow,wesm/arrow,xhochy/arrow,cpcloud/arrow,apache/arrow,laurentgo/arrow,kou/arrow,siddharthteotia/arrow,pcmoritz/arrow,tebeka/arrow,cpcloud/arrow,wesm/arrow,siddharthteotia/arrow,yufeldman/arrow,siddharthteotia/arrow,pcmoritz/arrow,kou/arrow,wagavulin/arrow,pcmoritz/arrow,apache/arrow,itaiin/arrow,xhochy/arrow,wagavulin/arrow,tebeka/arrow,siddharthteotia/arrow,icexelloss/arrow,kou/arrow,wagavulin/arrow,itaiin/arrow,xhochy/arrow,kou/arrow,siddharthteotia/arrow,renesugar/arrow,wagavulin/arrow,renesugar/arrow