This is a known issue in Hardware export when an external port is created.
In the HWH file, you can see that the APB related instance was set to _EMPTY_.
<MEMORYMAP>
<MEMRANGE BASENAME="C_S_AXI_BASEADDR" BASEVALUE="0x00000000" HIGHNAME="C_S_AXI_HIGHADDR" HIGHVALUE="0x0002FFFF" INSTANCE="ps7_ram_0" IS_DATA="TRUE" IS_INSTRUCTION="TRUE" MEMTYPE="MEMORY"/>
<MEMRANGE BASENAME="C_S_AXI_BASEADDR" BASEVALUE="0x00100000" HIGHNAME="C_S_AXI_HIGHADDR" HIGHVALUE="0x1FFFFFFF" INSTANCE="ps7_ddr_0" IS_DATA="TRUE" IS_INSTRUCTION="TRUE" MEMTYPE="MEMORY"/>
<MEMRANGE ADDRESSBLOCK="Mem0" BASENAME="C_BASEADDR" BASEVALUE="0x40000000" HIGHNAME="C_HIGHADDR" HIGHVALUE="0x40001FFF" INSTANCE="axi_bram_ctrl_0" IS_DATA="TRUE" IS_INSTRUCTION="TRUE" MEMTYPE="MEMORY"/>
<MEMRANGE ADDRESSBLOCK="Reg" BASENAME="C_BASEADDR" BASEVALUE="0x43C00000" HIGHNAME="C_HIGHADDR" HIGHVALUE="0x43C0FFFF" INSTANCE="__EMPTY__" IS_DATA="TRUE" IS_INSTRUCTION="TRUE" MEMTYPE="REGISTER"/>
</MEMORYMAP>
<PERIPHERALS>
<PERIPHERAL INSTANCE="ps7_ram_0"/>
<PERIPHERAL INSTANCE="ps7_ddr_0"/>
<PERIPHERAL INSTANCE="axi_bram_ctrl_0"/>
<PERIPHERAL INSTANCE
="__EMPTY__"/>
This issue is fixed in the 2015.1 release.
A patch is attached for Vivado 2014.4.
To use the patch, extract the zip file and assign a MYVIVADO environment variable with the path to and including the vivado\ directory.
See the included readme for more information.