envsetup.sh: add missing dquotes

Change-Id: Ic86a5dd36b0f32cd7dc4d2f9c187566398796ed6
diff --git a/envsetup.sh b/envsetup.sh
index 36ff220..13ea336 100644
--- a/envsetup.sh
+++ b/envsetup.sh
@@ -281,7 +281,7 @@
             PROMPT_COMMAND="echo -ne \"\033]0;${USER}@${HOSTNAME}: ${PWD}\007\";${PROMPT_COMMAND}"
         fi
         if [ ! -z "$ANDROID_PROMPT_PREFIX" ]; then
-            PROMPT_COMMAND=$(echo $PROMPT_COMMAND | sed -e 's/$ANDROID_PROMPT_PREFIX //g')
+            PROMPT_COMMAND="$(echo $PROMPT_COMMAND | sed -e 's/$ANDROID_PROMPT_PREFIX //g')"
         fi
 
         if [ -z "$apps" ]; then